Do not bring $100 bills with the serial numbers starting with “CB” into Costa Rica. You will have a difficult time trying to change the bills. Also, its probably not necessary to really change any money, especially at the airport (you’ll get ripped off). Just bring a lot of $1 bills. Businesses will give you change back in colones so you can use the change to pay in the future and you’ll get a better exchange rate.
The airport change booth gives about 10 to 15% less than almost anywhere else in the country.
Most of the supermarkets give current rates of exchange for dollars. if you want to change dollars in the bank , always have your passport with you as they will ask for it.