How long does a US passport have to be valid before entering Costa Rica?

Answer 1

The day your US passport is issued it is valid to enter Costa Rica.
If it is an old passport is must ramain valid for the lenght of your stay. Should you stay longer, and your passport is about to expire, you can have a new one issued at the US Embassy in Pavas, San Jose, Costa Rica. It is best to make a photocopy of the picture page just in case. Lost or stolen passports also can be replaced at the Embassy.
Enjoy Costa Rica >>>> it's a beautiful place with great people.

Answer 2

Some will try to insist that the passport must be valid for at least six months. In fact, it can actually be valid only for the length of time you expect to stay there, plus a day to get back home again. But for safety's sake it's still best if it's valid for at least six months in case of some unexpected emergency.

Here, by the way, are the requirements for travel to Costa Rica by US citizens:
Passport and onward/return ticket required. For stays exceeding 90 days, apply for an extension within the first week of visit with the Costa Rican Immigration Department and, after 90 days, obtain an exit visa.

Answer 3

The Costa Rican government requires your passport to be valid for 6 months from the day of your arrival. I am sure some slip by but I would not take the chance.