I was just in Key West and I enjoyed diving with Southern Point divers.
The Vandenberg is a great dive and I highly recommend you get a dive master to go with you. (They will make you have one if you are open water certified.) It’s a big wreck and you’ll need a guide to see the best stuff. If you are fairly inexperienced, give them a call first and make sure you are up to the challenge.
Molasses Reef near Key Largo is one of my favorites and a great place for newbies.
Finally, Christ of the Deep is also worth visiting just so you can say you’ve been there.