If you want to dive the Atlantic you'll be better situated on the north coast but if it's wrecks, walls, and caves you're looking for then the south east coast (think Bayahibe, Juan Dolio, Boca Chica) is where you'll want to be.
From any of these locations it's a quick trip to Dive at Embassy (wreck) the Tania V (wreck) or Las Galetas (wreck). The wall and the aquarium at Catalina Island is just a short trip also as are several cave/cavern dives near Boca Chica.
Any good dive shop can take you to most of the sites or you may want to hook up with a local PADI dive instructor to provide 'private' tours for your group (PM me if you want contact info for a couple).
Check out my DR1 Blog for some pic's of the underwater widelife and keep tuning into my blog as I'm just scanning some photos in and will be posting more dive pic's in the next 10 days or so.
<a href="http://dr1.com/blogs/?u=MommC" target="_blank">One Click will do!!</a><br /></div>
Here's a "teaser" for you