OP -- Depending on where you live, you might want to consider doing your classroom and Confined Water (pool) training at home and then do your OW dives (the "checkout dives" ) while on vacation. This can have two advantages:
a. Don't waste your vacation time in a classroom and/or in a pool learning the basic skills you can learn at home; and
b. Gives you an introduction to the local diving community -- which can be important IF you decide you actually like diving and decide to become a "regular" as opposed to "vacation" diver.
Also, don't worry so much about the water temps in the tropics -- the reality is that almost regardless of the water temp, you WILL get chilled if you are in the water long enough. The cure for that is proper exposure protection -- at least a 3mm wetsuit, or better yet, a 5mm full suit.