Probably the richest of the mainland Central American countries (and probably the only one of them that has mostly avoided violent coups or revolutions in the past). It's name even literally means “Rich Coast” in Spanish. Notable for abolishing its standing army already in the 1940s (and replacing it with a simpler National Defence Force). The country borders Panama in the south and Nicaragua in the north.
Costa Rica (or its rough territory) barely appears in alternate histories. Though one could argue Michael Crighton's Jurrassic Park series of novels and their film adaptations offer a somewhat AH-esque Costa Rica (e.g. it owns two fictional archipelagos that don't exist in OTL and there are mentions about the Costa Rican Air Force, of all things !).
None that we know of.