As another lactose intolerant person, I have to say I've never seen the Lactaid brand (or any other lactose-free brand) at any of the resort shops. They're pretty small shops and only carry a couple of regular kinds of milk. The alternative is to take a whole bunch of Lactaid tablets with you from home.
Pills it is. I love my Carnation instant breakfast in the morning and I can't rationalize spending the $40 minimum for Garden Grocer just so I can get Lactaid milk.