OK, you've gotten a lot of replies. May I offer an additional thought?
There's no better teacher than "experience", good or bad. No matter what the outcome of taking a lesson on a Catalina
22, you will come away with more more knowledge than you had when you started. It may be knowledge that improves your sailing, or simply knowledge of the Catalina 22, or both.
You may find, after sailing the 22 (which is great boat), that you like the "amenities" versus a 12' or 14' daysailor. The 22 is trailerable, so you are not committed to one lake or one marina, if that is your main concern.
However, I'd make one more suggestion. Go down to the marina in question, and start talking to some sailors about their boats and their experience. I ca't think of one sailor that doesn't like to talk about his/her boat! And, if you hit it off, you're likely to get offered a ride - and then you will get more "experience", and have another data point with which to make your decision.
I'd take the course if I were you. I'm self-taught for the most part, and can tell you that things like that will help you climb the learning
curve much faster than trail and error.