It's fairly difficult to get to the Caribbean from the west coast on the same day. For those itching to go to Jamaica, there was good news today from USAirways, which is launching a new nonstop route from Phoenix to Montego Bay. The new flight (which is seasonal, operating only from mid-December through mid-April) leaves Phoenix Friday through Monday at 10 AM and arrives in Jamaica at 4:53 PM. The flight from MoBay leaves Thursday through Sunday at 12:25 PM and arrives in Phoenix at 4:09 PM. It might still be possible to connect to a short hop on Air Jamaica if you were going to a different island. This is one of the very few flights to the Caribbean from the west coast (and the only nonstop to Jamaica since Air Jamaica canceled their LAX-MoBay flight).
American still offers twice-weekly service from LAX to San Juan on flights 238/239. The outbound LAX flight is an overnight leaving at 11:10 PM on Friday and Saturday nights, arriving at 9 AM; the return flight leaves San Juan at 10:25 AM and arrives back in LA at 3 PM on Saturday and Sunday.