This is true.
People dislike living on the islands because:
1. Sometimes the locals aren't terribly nice to non-natives.
2. Crime rates can be a bit higher (depending on what you're used to) and the police are... less helpful sometimes.
3. You are isolated from everyone and everything familiar, and the flight back is long and expensive, so visits are limited to 2-3x a year.
4. Everything costs a lot. I don't know about Grenada, but on St. Kitts, cereal is like $10 a box, milk is hard to get at all sometimes, and non-tourist clothes are nearly impossible to find... to name a few things.
5. Robberies happen (in St. Kitts) and there's not much to be done about it when they do... prevention is best, but they know American students might have good stuff in their apartments.
6. There's nowhere to go! No changes of scenery, no getting away... just a circle of coast around a few square miles.
That's what comes to mind as negatives for a place like St. George's. Acknowledging and accepting these things will be necessary to enjoy yourself in that kind of setting, but it's certainly not impossible! I'm sure there are good reasons (besides the view and the beach!) to attend an island school. And, SGU might be really different from Ross. Anyone from SGU care to comment?