We've done the trip several times with only carry-on, and that's me, my wife, and two girls, 24 & 22. They've all learned to travel light!!
However, the last couple of times, we've brought our own snorkeling gear, which gets pretty tough to do carry-on!
And since we were checking at least one bag, the last time we devoted one suitcase entirely to books (I live amongst a bunch of avid readers)!
I've found a $505 R/T on UsAir (ugh, oh well) and I think I'm going to pull the trigger.
tom
edit: price gone —.which isn't surprising. Guess I'll keep rollin' the dice a bit longer.