Well, I would say that a summer league sounds like something that might do you some good!
A lot of summer leagues are filled with "non-bowlers" just looking for a reason to get out and socialize. It really makes for an ideal time to work on your game or practice new techniques. Do you really want to work on something new during a fall league?
Of course you could skip a league and just practice occasionally, but it sounds like you might not stick to a practice schedule. It's sort of like getting a gym membership - its too easy to say "I'm too tired to work out today" or "I've got something else to" and then blow it off for a few weeks. With a league you have a commitment to the rest of the team, so it's sort of like a "forced practice."
That's just my 2 cents. You could just not bowl all summer, take up golf, tennis, or something else and then hope that come fall you find the desire to bowl again.