Marriottmillionaire,
What are the exact dates that you are looking for? Spring break varies from city to city. The Marriott hotels will only book 50 weeks out. Both the JW Marriott and Casa Magna Marriott in Cancun are available for award travel over the mid- February break, as well as from late March through early April, which I believe coincides more with your requested dates. Both of those properties are known to be wonderful.
Althouh I have not personally stayed at the Nassau, Bahamas Marriott I did stay at the Radisson next door, and the comments from Marriott guests were far less than flattering (food terrible, hotel in need of updating, no real beach, etc).
Do a search here for previous remarks about the St. Thomas location, if interested. Many have reported on it before.
If you are intersted in the April dates, now would certainly be the best time for you to book.