I love the Jet Blue option - if only...
Liat has the most flights into SVG from the hubs already mentioned (Barbados, Grenada
or Trinidad). Liat flights often don't show up on the regular booking sites, so check their website directly.
My favorite option is to fly into Barbados and then take SVG Air to St. Vincent. It costs about the same, but saves you having to go through customs
and re-check your bags. They will meet you when you land and direct you to their in - transit terminal. Way smoother than Liat.
It has been a few years since I have done it - based in Grenada
now. But if you can go SVG, it will be worth it.
Enjoy the Grenadines!