I went to Playa del Carmen earlier this summer at all-inclusive resort (oh yes, all you can eat buffets, unlimited alcoholic beverages, a la carte dining...) not a whole lot of exercise when everything you want/need is just a few steps away.
You know what the BEST advice someone gave me? "Eat what you want, but watch the portions." So I did just that - when I gave myself permission to eat what I wanted, I didn't feel restricted or start to "crave" things that maybe I normally wouldn't eat. I ate until I was satisfied each meal. Some meals I did try to choose better - eggs, etc. I was too scared to eat any of the fresh fruit lol. But I didn't get sick and I came back having maintained my weight so it worked!
Good luck...and have fun!!