Check out to see if the dates/departure cities are good for you but if they are, wow!!! $9 each way + taxes.
http://www.spiritair.com/welcome.aspx?pg=salesinformation&number=78

Even if you can't get these special fares, Spirit will continue to have very low fares (closer to somewhat less than $100 instead of the amazing $9) to and from MoBay from Ft. Lauderdale. And, Jet Blue is just one of the many low-cost airlines that fly into Ft. Lauderdale. So, you can probably still book relatively inexpensive flights to and from Jamaica after these really cheap fares are gone.