As some others do, I just take some leftover pesos from the year before and use them to get started upon arrival, then seek out the Mexico National Bank's ATM's.
There is some good info on Trip Advisor about currency. It also doesn't hurt to look up your resort on Trip Advisor to see what others experiences have been at said resort with any currency tips.
Just a little thing, but it's said that it's sometimes a little extra work for the Mexican people if tipping in Cdn. or US dollars. It means they have to go to a bank to exchange the money for Pesos. I just try and put myself in their shoes. If someone tipped me here in Pesos, it would take an extra trip to the bank to exchange for my own Country's currency.
I think it's just a lot easier for them to receive Peso's which is their own currency. Just my thoughts. Have a wonderful vacation!
Currency info here:
http://www.tripadvisor.ca/mgo-g150768-s601?rev=90
Check out your resort here:
http://www.tripadvisor.ca/
Edited by Kellye, 2015-12-10 10:56:03