Hey Jenn! We have yet to work at a Sandals resort as brides have been a bit worried about their rules on outside vendors. From what I've heard from fellow photographers, if you call them a friend/guest attending your wedding and just happen to be taking your photos, then you shouldnt' have a problem. It's a great idea to double check with your TA.
One way to work within your photography budget is yes to find a photgrapher to bring along with you. There are lots of us out there that are fairly new to destination wedding end and yet have YEARS of experience in wedding photography. Those just starting with DW's are likley to offer better deals (expenses, plus minimal extras) and offer you great coverage.
Another thing to keep in mind, is with your wedding being in 2010 you may be able to find another bride gettting married within the same week at the same venue that would be interested in sharing expenses to bring a photographer along.
Lots to think about, but please PM any of us and let us know if you have any questions!
I'm sure you'll find just the right photographer for you two!
Best of luck!