THAD,
Was there (at RR) this past October (yep - not long after the storm passed right over top of her!), and I will be there from March 26th thru April 3rd (yippie!)
The reefs there are fantastic. You will soon discover that this is the jewel of the Bahamas if you like deeper diving with an abundance of sea-life (duh - is there anyone who doesn't want that?). I liken the diving at San Sal as the best of all the diving in the Carribean and Bahamas.
The water temps will be hovering right around 80f at the time of year you mentioned.
I can't say enogh how much fun you all will have. I higly recommend it. When you go, please don't forget to let you're DM Jean-Paul (Morales) know that Jim & Audrey (his "lil' dive buddy") said hi and that we told you all about how much fun would be waiting for you!
PM me if you have any specific questions that I can help with.
PS - I'd recommend that you rent scooters one day (the last) and take a tour of the island - esp. the north end.
Peace out,
Jim