I used to fly down in the islands and flew side by side with this group a lot. I believe that they operate under the DCA (like the FAA but in Antigua/British flight rules). At the time I could not fly for them unless I transferred my licenses over. It's possible to transfer over after like 6 tests if I remember right. Not sure about a practical test. I think the tests were like taking the ATP written 3 times and then some A&P written exams. It was a pain in the ass.
Besides the conversion, the flying is amazing. Lots of short legs in a twin otter. I know they were looking at the DO 228 to fly in and out of St Barts (Air Guadeloupe had these too). You go to St. Kitts, Nevis (where I lived), St. Barts, Saba, all the cool islands. Short runways with one way in one way out. Lots of seat of the pants stuff that becomes routine after a month or so. At least they have gate agents so you wont have to deal with customs paparwork all the time (this is a real drag going to so many places a day).
I cant tell you much about the pay and I might be off on the regs (they could be French regulated too...cant remember) but I can bet that the pay is very low. I can imagine it's enough to live on down there but thats about it.
As far as 135 operators....San Juan is a dive...check Nevis Express if you want to experience the islands. I think they are still 135 anyway but I'm not sure. This is where I flew and it was an experience....I'll just say that.