I agree with all the previous replies.
Summer leagues are generally less serious (and also alot shorter) than winter leagues.
Summer leagues are finding it harder and harder to get bowlers, because people want to be outdoors and going to the beach and stuff on weekends in the summer. Especially on Fridays or the weekends.
There are some intersting summer league variations you can try, too, such as a no-tap league. In no-tap, you get a strike whenever you knock down 9 pins. It sounds easy, but I tried it before, and its not as easy as it sounds. Also, something to beware of with no-tap is that you will totally forget how to shoot all your single pin spares when you never have to do them, especially the 7 and 10 pins.
Many summer leagues also offer a ball option, where you can pay a few dollars extra each week and get a new bowling ball at the end.
But do not be intimidated by league bowlers. They range in average - some are very good, some are also just starting out. We're all people, too.
Try talking to the managaer at the bowling alley, or the guys who work the counter. They will direct you to a good league for you. Yes, some leagues are more serious, etc. But most are as social as they are competitive.
"Bowling should be played by bowlers, not physicists." - CoachJim