You also should be nervous about hiring a lawyer that does not encourage you to be entirely truthful with the government. If your attorney is not ethical in his or her dealings with the government, you can expect that he is not going to be ethical in his or her dealings with you. Besides, the government has an amazing ability to ferret out lies anyway. You should also be weary of lawyers claiming to have connections which get them special treatment. These claims are never true.
Immigration law is one of the only areas of law in the country which are strictly federal in nature.
This means that only the federal government can make immigration law, not state or local governments. The rules for processing an immigration case are the same anywhere in the country. Furthermore, most immigration procedures are handled via mail. The only time you definitely should consider hiring local counsel is in an immigration litigation matter where you will need representation in front of a judge. You can, of course, hire a national attorney for this, but the travel expenses could add significantly to the cost of the cas.