Frank, if it's shore diving you're looking for then I don't think anybody will disagree that you should spend it in the Fort Lauderdale area. Lauderdale by the Sea has been called the shore diving capital of the US, and motel rooms on or across the street from the beach are reasonable (anything on El Mar Drive will do). There's a Holiday Inn here with a straight shot to the beach.
Other options: there are also good shore dives in Hollywood and Dania. I don't think there's much north of here, and there's not much south, but you might also consider taking your chances on the weather and scheduling a day to head WEST to Venice to dive for fossilized shark's teeth (you'll get 50 your first try unless conditions are bad).
Not much "shore" in the keys to dive, though... it's mostly mangrove so there isn't much sand. There are little dive sites here and there but the boat trips are so much better almost nobody heads down for the shore diving.
Let us know when you'll be rolling in and watch this forum for group shore dives. You can pretty much find somebody anytime to dive here with you.
