You can probably do San Pedro on Ambergris Cay in Belize for 4k, but airfare could get you. (We usually plan on about 5k and bring some home. Once you get there you can have a blast doing snorkeling and fishing with some great seafood too. Conch and lobster! We do a week there, staying at Mata Rocks Resort. It is small and on the water, a little south of town, nice place that treats you right. We rent a golf cart for a week to get around and see the sights. If you get there ask about the Chicken Walk. Lots of fun...a big checker board on the floor that all the squares are numbered. The turn loose a chicken to walk around. You pick squares (for a buck or 2) kind of like roulette. When the chicken takes a crap, the number that gets dumped on wins!! The more you drink the more fun it gets. We are going back this February and are going to look at condos.
I do our traveling in the winter, gets us out of the cold weather. Its payback to my great wife of 48 years for my hunting trips. I have a great time, so its almost like double dipping for me.