PASSPORTS AND DOCUMENTATION
What documents do I need to travel to Costa Rica?
Your passport must be valid, and must keep validity for six months after your arrival. You will also need to show your flight ticket to leave the country. Presenting both things you will be stay in Costa Rica a maximum of 90 days.
If your flight stops in the United States, your passport must be machine-readable and you will have to apply for ESTA. Here you can find out how to do it: https://www.esta.es/.
As always, it's a good idea to send to yourself an email before you travel. Include in it the key information about passport numbers, insurance, telephone numbers and any other information that may be necessary to help you.