Last time I checked Movistar's coverage in Mexico wasn't all that great. If you are using it for a road trip, I would check it before choosing a carrier.
Interactive Coverage Map : Movistar (Telefonica), Mexico
Compare Telcel:
Interactive Coverage Map : Telcel (America Movil), Mexico
Telcel is more expensive, but has better coverage. My Spanish is no better than yours. Arrepentido ("sorry").