Thanks for the replies, everyone! I just got back from my trip to the Keys. Got my PADI Certification and had a good experience with Captain Hook's in Marathon. It was not the most recommended place, but the price was reasonable and as the only student in the program at that moment, I basically got private lessons. Can't wait to get more dives in--looks like my job is taking me to Belize in a couple of weeks, so that will be the next place I get in the water...