I'm with Isa on this one: knowing exactly how much I'll pay is what's driving my choice this trip. My only all-inclusive experience was pretty dull, but I'm hoping to find a more upbeat (although not a teenage free-for-all) place with interesting things to do besides water aerobics and Lambada classes at 9 a.m.
Cuba would be interesting - at least they let you visit!!
If possible, and I am sure there are some in Cuba (I'll look too), go for the "couples only" or "no one under the age of 16" resorts. The later are rarely over-run with teen-agers. (Or, so our experience has been...)
We have had both the boring and the exciting all-inclusive experiences, though more often than not, it's been really fun. But, we also make a point of getting to know the staff members which we enjoy a lot. Not only do we learn about the local residents and culture, they usually can tell us the more interesting (less touristy) things to do and see cheaply.
People bad-mouth all-inclsusives, but they do have their advantages depending on your time, money and location constraints. Not every A-I is filled with obnoxious tourists. We've met a lot of very nice people and have had some really fun vacations that way.
Again, good luck T!