If you want to avoid idiots, then why are you planning to spend a good deal of time with dive instructors?
As mentioned by
@THE Chariman, the Upper Keys are not nearly as big a magnet for the spring break crowd as other locales. Even in Miami and Ft. Lauderdale, few of the more festive and foolhardy party gang congregate aboard the dive boats.
The college kids that I’ve encountered tend to be relatively new divers or go to schools where access to diving is extremely limited if it exists at all. The vast majority of these young people are very excited and enthusiastic about the opportunity to dive, (“We’re way stoked to be here dude”), and have gone to some not small expense to take a class, rent gear, and book a charter or two. Some of these folks have been dreaming of these trips for quite a while, and have enough respect and basic understanding to show up sober, on time, and with at least a modicum of courtesy and dignity. Once you get back on land though, things can change immediately.
I’ve only visited Key Largo a few times for half-day dive charters since Hurricane Irma passed thru. I do not know the current status of the infrastructure that may effect your plans. I suggest that you contact the instructor or shop that you expect to train with, and see if they can advise you about any accommodations, services, and amenities that you will require.
As you’re planning a long stay
@Mindset, you might want to take advantage of the diving further north off of West Palm Beach, Jupiter, and etc. for a few days.