Unless I have to connect through an American city (Minneapolis, Atlanta, Dallas, Houston) and need to tip/buy something where a credit card won't work, I bring NO American cash. I exist solely from pesos acquired at one of my trusted ATMs. Has worked for me for at least a decade.FWIW, when I get to Cozumel, as soon as I can I change over to cash in pesos for everything but the hotel bill. I try to think in pesos as opposed to "how much is that in American money?". I go to an ATM that I trust as needed to charge my cash supply.
YMMV.