On satellite radio I'm not 100% sure; but my guess would be that XM would be your best bet. XM's satellites are in geosynchronous orbits; meaning from Earth they are always in the same place in the sky. So they orbit around the equator; on over the Atlantic and the other over the Pacific.
Sirius has 3 birds; and they appear from Earth to do a figure 8 over the Americas. While this may sound good in theory; I know that they turn off as they head south over Mexico, and turn back on heading North.
For footprints for US satellite; you may also be out of luck. Best place to double check for that would be satelliteguys.us
But I know I've read threads where people can't get Dish or Direct in parts of Mexico.
The reason for the footprints is two fold. The first; these satellites are only putting out a couple of hundred watts of power. If they focus the beam to a certain area they can provide better service. I know with Nimiq 1 when they re-aimed it towards Canada and people in Texas were left crying, I ended up with a signal that would survive a hailstorm. (For those in the know; please note I'm not talking about the Nimiq 3 activation a while ago.)
Edit- found a copy of the gif that shows how the satellite radios move. Don't look at it if you are drunk:
http://img122.imageshack.us/img122/3...ritrack6tg.gif