Nobody has offered with an on-point answer so I'll throw in a recommendation for Direct TV over Dish Network simply because the satellite is much easier to find when pointing your dish. A compass and a $30 satellite finder will save a lot of time, shouting, frustration and grief.
No experience with reception in Mexico. I know that the satellite television providers use spot beam transmitters for the local channels so you can't get them if you get too far from home. The other channels, though, should be available anywhere and when you first sign up you can get network feeds for east coast or west coast instead of local channels. You have to tell them it's for an RV and you have to sign some kind of waiver.