If you have wifi you can use skype which I believe is free to toll-free numbers and $0.02 per minute to any other US number.
The time it would take me to learn and manipulate some other system would not be worth it to save a few pennies per call.
I live in San Miguel de Allende, took my unlocked old I-Phone into a Iusacel store, and have a chip that's worked with pretty good coverage all over Mexico. Like Telcel you can purchase minutes just about anywhere. I picked Iusacel because a lot of people I know here recommended it, and the store is right next door to the pub where I go to watch the hockey games here in Mexico!
I use an ATT Go-Phone for Baja, excellent coverage, low rates. I load the phone with $50/yr, rarely use up the minutes. I don't use my phone much when in Baja, but I have been impressed with the coverage when I do need to use it.
Verizon coverage in Baja is almost non-existant.
Pre paid means no surprise phone bills when I get home, and if I lose the phone or it gets stolen it's not the end of the world.