RoamTheWorldCellPhones.com

Cellphone GSM Frequencies: 1800

(This means you will need a GSM cellphone that will work on 1800Mhz to use it in Costa Rica.)

Cellular carriers for Costa Rica

I.C.E. (Instituto Costarricense de Electricidad)

Frequency: GSM 1800
Website: www.grupoice.com

Coverage Map

If you've used either of these networks or roamed in Costa Rica, please post about your experience and the cost. Feel free to ask questions.