Is it possible to buy pre-paid cell phones at the airport?
Yes. Three of the major telephone companies in Costa Rica (Kölbi, Claro and Movistar) offer a pre-paid cell phone service at the airport, and also at any of their shops throughout the country. This system will work if you have an unlocked phone that uses replaceable SIM/GSM cards, as do AT&T and T-Mobile. Verizon, for example, does not use this technology so it would not work.
Costa Rica, as the companies have shops in all main towns. A Kölbi prepaid SIM chip costs $20 U.S.D. and includes 250 minutes for domestic calls, or roughly 65 minutes for international calls.