For your main trip may I recommend Old Providence? It is in the Western Caribbean. Although maybe a bit more expensive to get there, the accommodations are much cheaper than the larger resort destinations. So it all equals out as far as price and the diving is equivalent to some of the best know destinations. With the worlds 3rd largest reef with over 100 square miles you can almost never run out of dive sites. I have a trip scheduled for Memorial Day weekend with prices [ at ] $99/night. I could probable get the same rate if there was enough participation.