Many people on here will speak to the contrary about credit cards... but I don't find them useful for small purchases. Going out to dinner and/or a big Walmart run would be places I would use it. but for the markets, clubs, convenience stores, tipping, etc.. cash is king. I'm not even close to an expert. Hell, I've never even been to Cancun. But I did stay at a Holiday Inn Express last night.
USD $$ and pesos for me too .. I use my credit cards when booking excursions from the hotel etc so I can collect the points.
I bring a couple hundred bucks and take out a couple thousands of pesos from the ATM. I carry a little of each when I go out. Most places will accept both. I look at the exchange rate they use and decide which currency to use. Right now $1 = $10.75 pesos. So if the club promoter asks for 30 dollars or 300 pesos for the entrance, I give him pesos. If MickyD charges 5 dollars or 55 pesos for big mac meal, I pay in dollars.
