You can change money at a convenient casa de cambio (Money Exchange House). These are money exchangers that are open long hours and provide quick service. Although dollars are widely accepted in resort areas (and are often preferred), we recommend using pesos during your stay. Hotels also exchange dollars but these normally give you the lowest rates, use them as a last resort. You will find better rates at the exchange houses, and the best rates at banks.
To exchange money in the banks you can only do it between 9 AM and 1PM (even though the banks are open longer). Expect a slightly lower rate for travelers checks. Commissions are not generally charged on money exchanges. While foreign currencies other than U.S. dollars are sometimes accepted – particularly at major resorts—we recommend you use pesos during your stay.
We also recommend exchanging $20-$30 into pesos before leaving home. This way you will arrive in Mexico with pesos for cab fare to you hotel and for tipping. Also, carry $20 to $30 dollars in one-dollar bills — they are great for tipping and are quite appreciated.
Please see http://xe.com for current exchange rates.