When are you heading down? This week or the following? What type of diving are you looking to do? Are you going to have a boat, or go with one of the LDS?
I would suggest Captains Corner for what you want. They are in the heart of Old Town, and Leslie is AWESOME! Just tell her Phil sent you, and she will get you taken care of. I am one of her DMs, and can honestly tell you that she is the most diver friendly, least money hungry dive operator on the Island
Message me on here if I can help you out with anything while you are down here. I can suggest to you where to eat and where NOT to eat. And for the other things you want to do, I can get you set up with that through the best operators for what you want to do.
AVOID THE BOOKING BOOTHS ON DUVAL ST!! They are owned by the operators, and will book you on THEIR boats or whoever is paying them the highest commission for the day. I get nothing from anyone, and just want everyone who comes to my island to enjoy it.
Im actually trying to find people to go down THIS week if you could make it early. I have a 3BR townhouse set up through Sunday in Old Town and will be doing trips to the Vandenberg once she is down on Weds