The Costa Rican GSM cellular phones are now able to send and receive international SMS (short message text).
The ICE (Costa Rican Electricity Institute) is currently running a pilot plan to test the service. ICE is the only telecommunications provider in Costa Rica for cell phones, land lines and internet.
So far, the international messages are only available between the Costa Rican cellular phones and other five countries (USA, Mexico, Panama, Nicaragua and El Salvador).
I.e. to send a message to the US you use the number as:
00 + 1 + area code + phone number.