....back 15 years ago, I always exchanged Canadian (via American Express traveller's checks) directly to Mexican, Belizian, Guatemalan, Honduran, and Costa Rican currencies. There was one point in the mid '90s that Guatemala quit taking Canadian (and, any Amex TTs). Today with the advent of ATM and debit cards, I think virtually every Latin American banking ATM will accept any of the G20 country's currencies.
ATMs and debit cards are a whole different animal today for the "modern traveller", when compared to pre debit card days.