Where is a great, cheap tropical vacation spot?

I am looking to take my boyfriend on some sort of tropical vacation this summer for 4 days or so. He has never been anywhere outside of the continental US before, so I think somewhere like Bermuda may be really fun (though I have heard it is pricey there). However, I am not made of money and do not have loads to spend. I’d also like somewhere close to the US (I live in Maryland) so we wouldn’t waste too much time flying.

Any suggestions would be much appreciated. I’d love somewhere all-inclusive, but so far the ones I have looked at, like Sandals, are a bit pricey. Thanks so much!!