If you're interested in Spain (not the beaches) I have lots of info on my blog. Plenty of interesting history, great food, interesting culture. There are some very good tours if you don't speak Spanish.
Anyway, I also like Key West.
Spain has some great beaches but they're not in the mainland but in the Canary islands. There's an island called Fuerteventura with kms of white powder sand beach.
And believe me, I know Caribbean beaches well.
I have been to Aruba and to most Cuban beaches. Fuerteventura is really nice in that regard, but just that, you won't find an extremely developed island with lots to do.
On that part, lanzarote is a very peculiar interested volcanic island, it offers a great contrast in its landscape, you can see volcanic rocks , an almost lunar scenery, right next to white long beaches. Interesting island. Jose Saramago, the Portuguese writer, lived in lanzarote for many years until his recent death.
The Florida keys are wonderful, but beaches just don't compare to Aruba. Check out Hawks Cay Resort in Duck key Maraton. Lovely lagoon beach, great pool and one of the best buffet breakfasts I've ever experienced. You can take a walk after breakfast and watch the dolphins. If it's Key West you want it's only an hours drive and an easy day trip. In Key West there is also the Hyatt Botique Resort which is within walking distance of Duval St for shopping restaraunts etc. The beach at the Hyatt is quite small though.