Very few answers to the initial question. My advice is, do it. Get a snorkel and mask, practice in a pool or in shallow water when you get down there. Some dive operations here in the states also give snorkeling lessons. The snorkel trips we have been on in AC always have had a few newbies, and the operators usually handle them with great care. If you are just practicing in shallow water, there are always a bunch of more experienced people willing to help.
No matter what, if you've never done it, do it when you get the chance, it's a whole new world down there. It is not physically challenging, little effort needed other than developing a relatively simple technique.