The ATM's have 24 hour access, some of the hotels have them and the ones in town are easily accessible. The cambios however do not often give the same exchange rate as the ATM and are open much fewer hours. Travelers checks are definitely becoming a thing of the past and many bank chains do not any longer offer them as well I know I seen one boardie have trouble cashing Traveler checks last year when we stayed at same location and he was left struggling one night out with no way to get cash after having spent what he had on him even though he had tons of traveler checks. If you are worried about using your linked to bank account you can just get a VISA pre paid card from most any stores near home and use that.