<PAGE>

                                                                    EXHIBIT 10.4


           FIRST AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT
           --------------------------------------------------------


     This FIRST AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT (this
"Amendment") dated as of December 29, 1999, is entered into among (1) KSMS-TV,
 ---------
INC., a Delaware corporation, TIERRA ALTA BROADCASTING, INC., a Delaware
corporation, CABRILLO BROADCASTING CORPORATION, a California corporation, GOLDEN
HILLS BROADCASTING CORPORATION, a Delaware corporation, LAS TRES PALMAS
CORPORATION, a Delaware corporation, VALLEY CHANNEL 48, INC., a Texas
corporation, and ENTRAVISION COMMUNICATIONS COMPANY, L.L.C. ("Entravision"), a
                                                              -----------
Delaware limited liability company (each a "Borrower," and collectively, the
                                            --------
"Borrowers"), (2) the several banks and other financial institutions from time
 ---------
to time parties to the Credit Agreement referred to below (the "Lenders") and
                                                                -------
(3) UNION BANK OF CALIFORNIA, N.A., as agent for the Lenders (in such capacity,
the "Agent").
     -----

                                   RECITALS
                                   --------

     A.   The Borrowers, the Lenders and the Agent previously entered into that
certain Amended and Restated Credit Agreement dated as of November 10, 1998 (the
"Credit Agreement").  Capitalized terms used herein and not defined shall have
 ----------------
the meanings assigned to them in the Credit Agreement.

     B.   The Borrowers have requested that the Agent and the Lenders agree to
certain amendments and waivers under the Credit Agreement and the Agent and the
Lenders have agreed, in each case subject to the terms and conditions set forth
below.

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
herein contained, the parties hereto hereby agree as follows:

     SECTION 1.  Amendments to Credit Agreement.  The Credit Agreement is,
                 ------------------------------
effective as of the date first set forth above, hereby amended as follows:

     (a)  The following new definitions are added to Section 1.1 in appropriate
alphabetical order:

          "Laredo Mortgage Indebtedness": that certain debt of Entravision to
           ----------------------------
          the Laredo Mortgage Lender, in a principal amount not exceeding
          $2,000,000, secured by the Laredo Purchase Money Mortgage.

          "Laredo Mortgage Lender": the commercial mortgage lender extending the
           ----------------------
          Laredo Mortgage Indebtedness to Entravision.

          "Laredo Purchase Money Mortgage": that certain first-priority mortgage
           ------------------------------
          executed by Entravision in favor of the Laredo Mortgage Lender,
          encumbering the Laredo Real Property.
<PAGE>

          "Laredo Real Property": that certain real property to be owned by
           --------------------
          Entravision and located in Laredo, Texas for use in connection with
          the operation of KLDO-TV, Laredo, Texas.

     (b)  Section 5.14(b) is amended in its entirety to read as follows:

          "(b)  Notwithstanding the foregoing, Entravision shall be entitled to
     acquire the KNVO Real Property and the Laredo Real Property without
     complying with Section 5.14(a)."

     (c)  The last sentence of Section 6.1(d) is amended in its entirety to read
as follows:

     "Notwithstanding the foregoing, expenditures made by Entravision for the
     purchase of the KNVO Real Property and the Laredo Real Property shall not
     be included as Capital Expenditures for determining compliance with this
     Section 6.1(d)."

     (d)  Section 6.2(i) is amended in its entirety to read as follows:

          "(i)  the KNVO Mortgage Indebtedness and the Laredo Mortgage
     Indebtedness;"

     (e)  Section (i) is amended in its entirety to read as follows:

                (i) the KNVO Purchase Money Mortgage and the Laredo Purchase
          Money Mortgage, provided that each (x) shall secure only the KNVO
          Mortgage Indebtedness and the Laredo Mortgage Indebtedness,
          respectively, and (y) shall not be spread to cover any other property;
          and

     (f)  Section 6.7(a) is amended by deleting the word "and" before clause
(E), substituting a "," therefor and inserting the following at the end of
clause (E):

     "and (F) the purchase by Entravision of Stations KATH(FM) and KOFX(FM), El
     Paso, Texas from Magic Media, Inc. (provided that the Consideration does
                                         -------- ----
     not exceed an aggregate of $14,000,000, plus closing costs and proration
     expenses)"

     (g)  Section 6.7(f) is amended by deleting "$7,500,000" and substituting
"$15,000,000" therefor.

                                      -2-
<PAGE>

     SECTION 2.  Waiver.  (a) The Borrowers have informed the Agent and the
                 ------
Lenders that they anticipate that the Maximum Total Debt Ratio for the fiscal
quarter ending December 31, 1999 will be exceeded, and have requested that the
Agent and the Lenders waive such requirement. Subject to the fulfillment of the
conditions set forth below, the Agent and the Lenders agree to waive, as of the
date first set forth above, the requirement under Section 6.1(a) that the
Borrowers maintain a Maximum Total Debt Ratio as of the end of the fiscal
quarter ending December 31, 1999 of not more than 6.50:1; provided, however,
                                                          --------  -------
that the Borrowers shall not permit the Maximum Total Debt Ratio as of the end
of such fiscal quarter to exceed 7.50:1.

     (b)  On December 22, 1999 the Borrowers borrowed $7,000,000 in Revolving
Loans for the purpose of making an Escrow Deposit. Such Escrow Deposit was made
by the Borrowers in connection with the anticipated purchase by Entravision of
ten FM radio stations, seven AM radio stations, three FM translator stations, a
Hispanic newspaper and a Hispanic radio network from Latin Communications Group
Inc. (the "LCG Acquisition"). The borrowing of such Revolving Loans caused the
           ---------------
Borrowers to be in Default of Section 6.1(a), as a result of their
representation upon such borrowing deemed made pursuant to Section 4.3(a).
Subject to the fulfillment of the conditions set forth below, the Agent and the
Lenders agree to waive such Default as of the date first set forth above;
provided, however, that the Borrowers shall not permit the Maximum Total Debt
--------  -------
Ratio as of the end of the fiscal quarter ending December 31, 1999 to exceed
7.50:1.

     (c)  The foregoing waivers are given in this instance only.  The foregoing
waivers shall not be construed as a waiver of or consent to any violation of, or
deviation from, any other term or condition of the Credit Agreement or any other
Loan Document, nor shall they be construed to evidence the willingness of the
Agent or the Lenders to give any other or additional waiver or consent, whether
in similar or different circumstances.  In addition, nothing in this Amendment
shall be construed to constitute the consent by the Agent or the Lenders to the
consummation by the Borrowers of the LCG Acquisition, it being understood by the
Borrowers that such transaction may not be consummated without prior consent in
accordance with the terms of the Credit Agreement.

     SECTION 3.  Conditions to Effectiveness.  This Amendment shall become
                 ---------------------------
effective as of the date first set forth above upon receipt by the Agent of the
following, in each case in form and substance satisfactory to the Agent:

     (a)  this Amendment, duly executed by the parties hereto; and

     (b)  evidence of the Guarantors' consent (provided that delivery of the
consent of the Luery Trust shall be on a best efforts basis) to this Amendment
on the signature pages hereto.

     SECTION 4.  Representations and Warranties.  Each Borrower hereby
                 ------------------------------
represents and warrants, for the benefit of the Lenders and the Agent, as
follows: (a) such Borrower has all requisite power and authority to execute,
deliver and perform its obligations under this Amendment, and to perform its
obligations under the Credit Agreement, as

                                      -3-
<PAGE>

amended by this Amendment; (b) all actions, waivers and consents necessary or
appropriate for such Borrower to execute, deliver and perform this Amendment,
and to perform the Credit Agreement, as amended by this Amendment, have been
taken and/or received; (c) this Amendment, and the Credit Agreement as amended
by this Amendment, constitute the legal, valid and binding obligation of such
Borrower (jointly and severally with the other Borrowers) enforceable against it
in accordance with the terms hereof; and (d) the execution, delivery and
performance of this Amendment, and the performance of the Credit Agreement as
amended by this Amendment, will not (i) violate or contravene any material
Requirement of Law, (ii) result in any material breach or violation of, or
constitute a material default under, any agreement or instrument by which such
Borrower or any of its property may be bound, or (iii) result in or require the
creation of any Lien upon or with respect to any properties of such Borrower,
whether such properties are now owned or hereafter acquired.

     SECTION 5.  Reference to and Effect on the Credit Agreement and the Other
                 -------------------------------------------------------------
Loan Documents.
--------------

     (a)  Upon the effectiveness of this Amendment, each reference in the Credit
Agreement to "this Agreement," "hereunder," "hereof" or words of like import
referring to the Credit Agreement, and each reference in the other Loan
Documents to "the Credit Agreement," "thereunder," "thereof" or words of like
import referring to the Credit Agreement, shall mean and be a reference to the
Credit Agreement, as amended hereby.

     (b)  Except as specifically amended herein, the Credit Agreement and all
other Loan Documents are and shall continue to be in full force and effect and
are hereby in all respects ratified and confirmed.

     (c)  The execution, delivery and effectiveness of this Amendment shall not
operate as a waiver of any right, power or remedy of the Agent or the Lenders
under the Credit Agreement or any other Loan Documents, nor constitute a waiver
of any provision of the Credit Agreement or any other Loan Documents, except as
specifically set forth herein.

     SECTION 6.  Execution in Counterparts.  This Amendment may be executed in
                 -------------------------
any number of counterparts and by different parties hereto in separate
counterparts, each of which when so executed and delivered shall be deemed to be
an original and all of which taken together shall constitute but one and the
same agreement.

     SECTION 7.  Governing Law.  This Amendment shall be governed by, and
                 -------------
construed and interpreted in accordance with, the laws of the State of
California (without reference to its choice of law rules).

                                      -4-
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and delivered by their proper and duly authorized officers as of
the day and year first above written.

                              BORROWERS
                              ---------

                              KSMS-TV, INC.

                              By: /s/ Walter F. Ulloa
                              Name:   Walter F. Ulloa
                              Title: President

                              TIERRA ALTA BROADCASTING, INC.

                              By: /s/ Yrma G. Rico
                              Name:   Yrma G. Rico
                              Title: President

                              CABRILLO BROADCASTING CORPORATION

                              By: /s/ Philip C. Wilkinson
                              Name:   Philip C. Wilkinson
                              Title: President

                              GOLDEN HILLS BROADCASTING CORPORATION

                              By: /s/ Walter F. Ulloa
                              Name:   Walter F. Ulloa
                              Title: President

                              LAS TRES PALMAS CORPORATION

                              By: /s/ Walter F. Ulloa
                              Name:   Walter F. Ulloa
                              Title: President
<PAGE>

                          VALLEY CHANNEL 48, INC.

                          By: /s/ Walter F. Ulloa
                          Name:   Walter F. Ulloa
                          Title: Chairman and Chief Executive Officer

                          ENTRAVISION COMMUNICATIONS COMPANY, L.L.C.

                          By: /s/ Walter F. Ulloa
                          Name:   Walter F. Ulloa
                          Title: Chairman, Chief Executive Officer and Managing
                          Member

                          By: /s/ Philip C. Wilkinson
                          Name:   Philip C. Wilkinson
                          Title: President, Chief Operating Officer and Managing
                          Member

                          AGENT
                          -----

                          UNION BANK OF CALIFORNIA, N.A., as Agent

                          By: /s/ Lena M. Bryant
                          Name:   Lena M. Bryant
                          Title: Vice President

                          LENDERS
                          -------

                          UNION BANK OF CALIFORNIA, N.A.,
                          as a Lender

                          By: /s/ Lena M. Bryant
                          Name:   Lena M. Bryant
                          Title: Vice President

                          CIBC INC., as a Lender
<PAGE>

                          By: /s/ Harold Birk
                          Name:   Harold Birk
                          Title: Executive Director CIBC World Markets Corp. As
                          Agent

                          FIRST UNION NATIONAL BANK, as a Lender

                          By: /s/ Wendy E. Klepper
                          Name:   Wendy E. Klepper
                          Title: VP

                          ABN-AMRO BANK N.V., as a Lender

                          By: /s/ David C. Carrington
                          Name:   David C. Carrington
                          Title: Vice President

                          By: /s/ Frances O'R. Logan
                          Name:   Frances O'R. Logan
                          Title: Senior Vice President

                          FLEET BANK, N.A., as a Lender

                          By: /s/ Sharon Hawkins
                          Name:   Sharon Hawkins
                          Title: Assistant Vice President

                          CITY NATIONAL BANK, as a Lender

                          By: /s/ David C. Burdge
                          Name:   David C. Burdge
                          Title: Senior Vice President
<PAGE>

                          THE CIT GROUP/EQUIPMENT FINANCING, INC.,
                          as a Lender


                          By: /s/ J.E. Palmer
                          Name:   J.E. Palmer
                          Title: Assistant Vice President


                          PARIBAS, as a Lender


                          By:________________________________________
                          Name:______________________________________
                          Title:_____________________________________


                          THE BANK OF NOVA SCOTIA, as a Lender


                          By: /s/ Ian A. Hodgart
                          Name:   Ian A. Hodgart
                          Title: Authorized Signatory


     Each of the undersigned, as a "Guarantor" under the aforementioned Credit
Agreement hereby consents to the foregoing First Amendment to Credit Agreement,
and hereby confirms and agrees that the Loan Documents executed by him, her or
it are and shall continue to be in full force and effect and are hereby ratified
and confirmed in all respects except that, on and after the date first set forth
above, each reference in such Loan Documents to "the Credit Agreement,"
"thereunder," "thereof," "therein" or words of like import referring to the
Credit Agreement shall mean and be a reference to the Credit Agreement as
amended by said First Amendment to Credit Agreement.


/s/ Walter F. Ulloa
------------------------------
WALTER F. ULLOA


/s/ Philip C. Wilkinson
------------------------------
PHILIP C. WILKINSON
<PAGE>

/s/ Paul A. Zevnik
---------------------
PAUL A. ZEVNIK


/s/ Richard D. Norton
---------------------
RICHARD D. NORTON


/s/ Yrma G. Rico
---------------------
IRMA RICO


KEVIN GRENHAM and STEVE G.
ROWLES, Co-Trustees of THE PAUL
A. ZEVNIK TRUST dated November
2, 1996, a trust formed under the laws
of the District of Columbia


By: /s/ Kevin Grenham
    Kevin Grenham, Co-Trustee


By: /s/ Steven G. Rowles
    Steve G. Rowles, Co-Trustee


EDITH SEROS, as Trustee of THE
WALTER F. ULLOA TRUST OF
1996, a trust formed under the laws of
the State of California


By: /s/ Edith Seros, Trustee
    Edith Seros, Trustee
<PAGE>

PHILIP C. WILKINSON and WENDY K.
WILKINSON, as Trustees of THE 1994
WILKINSON CHILDREN'S GIFT TRUST,
a trust formed under the laws of the
State of California


By: /s/ Philip C. Wilkinson
    Philip C. Wilkinson, Trustee


By: /s/ Wendy K. Wilkinson, Trustee
    Wendy K. Wilkinson, Trustee


PHILIP C. WILKINSON and WENDY K.
WILKINSON, as Trustees of THE
WILKINSON FAMILY TRUST, a trust
formed under the laws of the State of
California


By: /s/ Philip C. Wilkinson
    Philip C. Wilkinson, Trustee


By: /s/ Wendy K. Wilkinson, Trustee
    Wendy K. Wilkinson, Trustee


CAROL KRUIDENIER LUERY TTE,
CAROL K. LUERY REVOCABLE
TRUST UA DATED 7/27/98


By: ________________________
    Carol Luery, Trustee


ENTRAVISION HOLDINGS, LLC


By: /s/ Walter F. Ulloa
Name:   Walter F. Ulloa
Title: Chairman and Chief Executive Officer
<PAGE>

ENTRAVISION-EL PASO, L.L.C.


By: /s/ Walter F. Ulloa
Name:   Walter F. Ulloa
Title: Chairman and Chief Executive Officer

ENTRAVISION, L.L.C.

By: /s/ Walter F. Ulloa
Name:   Walter F. Ulloa
Title: Chairman and Chief Executive Officer


ENTRAVISION COMMUNICATIONS
OF MIDLAND, LLC


By: /s/ Walter F. Ulloa
Name:   Walter F. Ulloa
Title: Chairman and Chief Executive Officer


ENTRAVISION MIDLAND HOLDINGS, LLC


By: /s/ Walter F. Ulloa
Name:   Walter F. Ulloa
Title: Chairman and Chief Executive Officer


LOS CEREZOS TELEVISION COMPANY


By: /s/ Walter F. Ulloa
Name:   Walter F. Ulloa
Title: Chairman and Chief Executive Officer


COMERCIALIZADORA FRONTERA NORTE,
S.A. DE C.V.


By: /s/ Walter F. Ulloa
Name:   Walter F. Ulloa
Title: Chairman and Chief Executive Officer