no hay problema
Tel Cel have the monopoly in Mexico. You can buy a Mexican SIM card for most USA phones. (if your phone is unlocked)
Or, buy a cheap "pay as you go" phone once in Mexico. They have Tracfone, works pretty well and CHEAP. Cell phone Kiosks everywhere in border towns like Tijuana. The kids there are wizards and can get you set up. (they did me anyway)
Good news is you see Cell towers everywhere along Mex 3 and Mex 1 highways. Like many developing countries, they skipped that infrastructure step of telephone poles (in some rural places anyway).
Should not be a problem ... and as mentioned WiFi is now everywhere. I had no problems getting on line in La Paz, Capo probably even better.