We went to Curacao (2.5 hour flight from Miami) and loved it, we stayed at the gorgeous, four-star Kura Hulanda Resort in Willemstad and got an amazing deal because it was October, which is their low season. (The nice thing about Curacao is that it’s really too far south for hurricanes, even during the low season.)
That said, our idea of affordable may be way off from yours as we were a two-earner couple at the time – I think we paid $2000 for hotel and flight combined through Expedia.com (we got a free Honeymoon upgrade by e-mailing the hotel), then about $1000 more for incidentals on the island during our one-week stay. And we spared no expense on the island, let me tell you – for the whole week, we agreed not to track spending and ate wonderfully at the best restaurants, tried every activity available and drank fine, fine wine. Still, I think our week’s expenses came out to like $897. So we came out under $3000 total for everything including travel.
If I was looking to go really dirt cheap, I’d stay in-state, drive, and find a beautiful bed-and-breakfast for maximum privacy and atmosphere (and free breakfast, duh! :)), then spend most of my time in the bedroom. You can find some cute B&Bs in the Keys, and anything outside of Key West tends to be more affordable (aka Marathon, etc.).
Good luck and congratulations! I hope your wedding, honeymoon and marriage are everything you’re praying for!