Thanks for the links! That yahoo one is very recent.
You don't need a US passport to get into a US territory in the Caribbean (Puerto Rico, St Croix, St John or St Thomas). BUT, the new law that took effect on Jan 23, 2007 says it requires you to have a passport to get back into the US when you return. I would go with what the airline says... You don't want to get to the airport and have them turn you away!!
I think I got mine within 2 or 2.5 weeks when I had to have mine expedited I would do it just for piece of mind - and hey, if you ever do wanna go anywhere internatinoal, you'll already have your passport!
Puerto Rici is not inside of the US