This is probably much too late for Kathleen, but perhaps it will help someone else. If you are flying to Costa Rica from the WEST coast, do NOT let them book you through Miami! There are direct flights from Los Angeles to San Jose, Costa Rica with no change of planes. They take only a bit longer than the flights from Los Angeles to MIami, but there is no time wasted in Miami airport, and no continuing flight.
Most of them are red-eye flights, but we don't mind that, for you board the plane, eat your dinner, go to sleep with the help of a little melatonin, and wake up at your destination. It certainly beats the six hour flight to Miami, a 3-5 hour layover there, and an onward flight of four or five more hours.