Shifting on a derailler bike is pretty easy. You don't actually have the number of speeds it claims. Instead, think of the bike as having "uphill" speeds and "downhill" speeds (for a bike with 2 big chainrings in the front) or "hill", "normal" and "downhill" speeds (for a bike with 3 chainrings in front). So about 90% of the time, you just change the back gears. You only change around in the front if the terrain changes.

Florida is supposed to be very flat. You can probably get by with a single speed bike very easily there. The hilly bits in CT will call for more gears... how much, I'm not sure. A lot depends on how strong you are and how much biking you get in.

I wouldn't bother trying to go for a chainless bike. They're not common, and it's tough to find one that's more than a 3 speed.

If you decide to go for a folding bike, I'd make your decision based on customer service. Bike Friday doesn't have a lot of dealers, and is supposed to be very good at helping customers without a good local bike shop. Dahon seems to be a better choice when you have a local bike shop that sells lots of Dahons and is used to their quirks. So if you are at school most of the time and have a nearby (walking or city bus ride away) Dahon dealer, they'd be a decent choice. Both Bike Friday and Dahon sell bikes that should work in CT as well as in FL.