Each of them has a formal one that wouldn't allow jeans. Unless you were going horseback riding at CTI though, why wear them? It's sooooo hot there; I'd opt for something cooler, but you can wear them at most.
We don't even take jeans for the horseback riding. We just take longer shorts LOL. The jeans go into the suitcase when we get there, and we throw them back on for the trip home. (We travel in January, so that is the ONLY reason jeans get to go on the trip LOL)
Even though you may live in your jeans whereever you're from, please don't take room in your bag packing an extra pair. Just wear your jeans on your plane ride to Jamaica. That way you'll be comfy on your plane ride both ways. You can wear jeans at any restaurant that is NOT reservation only, but I'm betting after wearing your jeans once you'll decide that it is just too hot and humid to do it again. But maybe not, YMMV. Just remember that you cannot expect to get into any of the reservation restaurants wearing jeans, and you'll be all set.