Although credit cards are becoming more and more useful in Mexico, generally, only the more expensive hotels, restaurants and shops accept credit cards. You can use your ATM card in bank machines all over Mexico, so cash is always an option. The crime rate in the area is very low, so carrying cash is not a problem. There is an advantage to using your credit card, since it insures that you get the best exchange rate for that day.
One reason credit cards are not widely accepted is that many businesses do not have telephone lines so they cannot validate the card. Some places will charge you a percentage to use your card since they are charged a fee by the credit card company for the transaction.
If you use your card, be sure to check your
next statement carefully. As with anywhere in the world, fraud can occur, either by changing the amount charged, charging it in dollars when you signed for pesos, or by misusing your number to make other purchases. To be safe, write "in pesos" by the total box and keep your copy of the form. That way you can protest if there are problems with your bill.
Remember, a few places charge a percentage extra if you use your credit card, will give you a discount for cash, or will tell you over the phone that they take cards, but then tell you they credit card system is down when you get there. So always have some cash as a backup.
Larger grocery stores (San Francisco, Chedraui, Commercial Mexicana) take credit cards (MC/Visa) without hassle. Gas stations do not take cards at all.