Definitely a hard decision to make, especially since your wife wouldn't be able to join you at SGU. I'm not too familiar with the other programs you listed, but if they're carribean schools, you have the highest probability of coming back to the states if you go to SGU. Unlike a lot of schools like Ross, AUA, etc. SGUs stats are pretty solid and reliable. Not to say your time in Grenada won't be tough, I've just started CFP [charter foundation] here and it's definitely not like the US but from my roommates reports about their friends and family, other schools aren't as reliable as SGU nor guarentee you great spots.
Whichever choice you make, you're going to have to ROCK your grades in whichever route you go, because even if you went to a domestic school, if your grades are poo, youre not going anywhere. Going Carribean will be harder to place and more competitive, but you do well here, you can go to a lot of places in the US.