Wolfman didn't actually live in Mexico - that is just where the transmission equipment was located. He lived in the USA where he created his shows, but the actual broadcasts into the airwaves were generated in Mexico where the "Border Buster" transmitters and towers were located. Rush, or anyone else could probably apply the same methodology.
The advantage of transmitting from Mexico is it's proximity to the USA and the atmospheric "skip" patterns that bring the radio waves back down in the heavily populated areas of the US.
If (when) people like Rush were driven to this point by a tyrannical Obama government they could afford the technical expertise to determine favorable broadcast locations as well as obtaining the latest high powered transmission equipment.
Like you, I wouldn't be at all surprised to see a lot of continuing government effort to shut down avery source of Obama critisism. They aren't very subtle right now, but just wait until they decide to actually grab control of the last vestiges of the free media!
They didn't let laws and contracts stop them from rolling over the financial industry and stealing GM for the labor unions and they won't let laws or the constitution stop them from shutting down free speech.