Are there classes for learning how to cycle for exercise? Is there such a thing as a class that teaches people how to optimally ride a bicycle for exercise? This class would assume that a person "knows how to ride a bike" but that's about it (i.e. they can balance while riding the bike and they have some idea of what changing the gears does but that's all).

If such classes exist, how can I find one in my locale?
I would check with your local bike shops and clubs, there are lots of cycling "coaches" out there that will tell you exactly what you should be doing to get the most out of it. Essentially the personal trainers of the bike world.

I would also recommend doing some reading on optimal heart rate and zones. Coaches and classes can be expensive but if you read up on it you can do a lot of the same with a cycling computer and heart rate strap. However you may find that joining a "no drop" group ride could be equally beneficial as a starting point as they will offer advice as well.

Also, less related but I see you're in GA but down here in TX, we just started getting these places called Cyclebar ( http://cyclebar.com ) They play loud music and have and instructor and lighting effects, but they also track every aspect of your workout and can custom tailor it so that you get the most out of your training. All while in a group similar to a spin class but in the atmosphere of a club or bar(minus the drinking :P) They are suppose to be really fun and a good work out. I have yet to try it myself but it has definitely intrigued me.