Date: 201511
Local time of day: 1201-1800
Location: MMSD.Airport, FO
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Tower MMSD
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Less Severe
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Issued New Clearance
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: During International departure from MMSD (SJD); SJD Clearance Delivery; Ground; and Tower were all being conducted on frequency 118.9 by one Air Traffic Controller; on one of the busiest (traffic) days I've seen at SJD; with landings and departures being conducted to Runway 34.  We started and taxied uneventfully (although radios were very congested) to Runway 34 and were #3 to takeoff with several arrivals. While eventually holding short of Runway 34 number 1 to go; Company called for clearance; and Tower replied for us to hold short of the runway. It was very obvious he was task-saturated and getting confused running three frequencies. As well; the Controller reverted to Spanish working some of the other local traffic at times. Another carrier then called for clearance and the Tower Controller finally pushed them to a separate clearance frequency. During all of this; as aircraft landed; the Controller told each to bypass Taxiway C (NOTAM'd closed) and clear at Taxiway D. As we held #1; Air Carrier Y landed and rolled out on the runway; with another aircraft five to seven miles out; Tower asked if we were ready to go; which we replied affirmatively. Tower then said; 'Company # cleared for takeoff Runway 34; do not delay; traffic on final.' My FO replied; 'Cleared for takeoff Runway 34;' but as we took the runway; I noticed the previous Air Carrier Y had begun clearing at Taxiway C (Tower said something to him in Spanish) and then turned back nose pointed west then back north on Runway 34. I watched all this transpire and never pushed the power up to take off; but set the brakes; telling my FO we weren't going anywhere until the runway was clear and we were re-cleared for takeoff. Once the runway was cleared by the previous carrier on Taxiway D; and cleared for takeoff again by Tower; we departed uneventfully. I'm not sure how close the traffic on final got; but once we were safely away from SJD and at altitude; I sent Dispatch a message to forward to Company ATC and Safety personnel; and any follow-on Company arrivals to make them aware of the ATC safety issues happening at SJD. Had the visual conditions been worse; a Ground collision on takeoff would most certainly have resulted.Our vigilance today; along with some good visual lighting conditions; probably prevented a very dangerous situation from happening (which I honestly believe any other Company Pilot would have also seen and prevented in the same circumstances). SJD ATC was definitely in over their heads today and very task-saturated.


Second narrative: Cabo Tower needs to pass the Ground and Clearance duties to other frequencies on very busy travel days.


Synopsis: B737 flight crew reported they were cleared for takeoff with an aircraft still on the runway because MMSD ATC was overwhelmed with traffic with one Controller working three frequencies.