"Casas de Cambio," as the signs will read in Mexico, are plentiful in locations frequented by foreigners and offer rates that are often more competitive than at banks. Check several before choosing an exchange house as rates vary depending on the different institutions' demand for different currencies. Although a few exchange houses operate late, the vast majority do not, so they are best visited during business hours.
Although retail banks entail slightly less favorable exchange rates than exchange houses and the process of exchanging is more cumbersome, longer open hours could make them your best option. Banks are easily found in Mexico's towns and cities whether you are on or off the tourist trail. Keep in mind that some retail banks will only change foreign currency if the customer has a local bank account. Also, some banks have limited hours each day for exchanging foreign currencies. Look for the "foreign exchange" window or annex room beside the bank's lobby for a more efficient exchange process. If there is no such window or annex, be prepared to wait in a line (two lines for exchanging traveler's checks) for anywhere from a few minutes to over an hour.
If a favorable exchange rate is your primary concern, use hotels to exchange money as a last resort. As a rule, hotels in Mexico offer less favorable exchange rates. If you must, only exchange what you'll need until you can reach an exchange house or bank.
Exchange houses in Mexico's major airports, particularly Mexico City's International Airport, have rates comparable to those in the cities, so it's a good idea to take advantage of them.
