I agree with Briansue. Unless you have a CC that does not charge the international fee you will pay from 2 to 3% extra. Many merchants will charge up to 5% extra in Mexico if you use a CC. Even Costco charges extra. Re Santa Anna ATM. There used to be an ATM in Santa Ana that had parking. It has been closed and you have to go downtown. One can hardly get a car in that area. Forget taking an RV. Credit card fraud is rampant in Mexico. I have know too many visitors that have had problems. Even though you are not responsible for the charges it is a PIA when you are in a foreign country.
Moisheh