We've been traveling exclusively with Jet Blue from Boston. They have a non-stop from Boston in high season only, however, I've connected thru SJU and the gate from Boston is directly next to the gate for SXM so it was cinchy. The return, not so hot. Not J.B.'s fault.....it's the SJU airport is so huge and the International terminal is very far from Immigration/Customs. If you have any walking issues I strongly suggest requesting a wheelchair.
RE: cheap flight on J.B.....good luck. I haven't gotten a good fare with them in a couple of years. We pay the price for the service. We do love the non-stops.
Good Luck and enjoy SXM.

<img src="http://www.traveltalkonline.com/forums/images/graemlins/handshake.gif" alt="" /> Contessa