Most of the time you can pay for things with Mexican pesos but for rent, art or cooking classes often the cost is in USD. I recommend setting up a United States dollar cheque account before leaving so you will have cheques to pay in American funds.
When a cheque is not accepted it is great to have this site bookmarked on your tablet or unlocked smartphone so you can use the current rate of exchange to convert the USD amount into pesos. Be aware that there will be bank fees involved and if you are taking pesos out of your Canadian account for example there will likely be a slight discrepancy between the posted rate and what emerges from the bank machine due to local transactional banking fees added to your banking fees.
Seems everyone wants a piece of the ever shrinking peso pie!