I do have to correct one thing... while we are indeed part of the United States -- begrudgingly, some days -- we do NOT have a Wal-Mart. God willing, we never will.
Thanks for the baggage weight info -- my dad's coming down, and I'll have to warn him to limit his gear. :)
Definitely do pack light. The emphasis should be on light, airy and quick-drying clothing, which comes in handy both on the water and in our rather sticky climate. You also might want to pack extra swimsuits, because it's unlikely that one will dry completely overnight. If you're really sensitive to the sun, you may want to have a light long-sleeved shirt if you're going to go out on the water. Don't forget a hat of some kind, and don't skip on the sunscreen!
While flip-flops are perfectly acceptable footwear, I usually opt for a comfy and sturdy pair of Tevas because we walk a lot.
More advice than you probably need, but forewarned is forearmed!