I know a guy who actually worked for the PBA tour, a darn good bowler (240+) but he never tried to go pro, or bowl in the pro tourney's. He recently decided to go back to school and still maintained his eligibility.
As for bowling against adults, when you join the league, don't brag or talk up your game because unless your in a very weak bowling area, you'll likely be middle of the pack at best once you make the jump. Nothing wrong with being confident, but most university bowling teams have a very difficult time winning leagues due to the calibur of bowlers. Let your game do the talking, after you've established yourself, then you can start to joke around and trash talk. Otherwise you'll rub people the wrong way.
I actually started bowling in adult leagues when I was 15 because there was no youth programs worth mentioning in my area at the time, and truly loved the experience. I knew most of the bowlers would be better, more experienced, and took the opportunity to learn from them. Most bowlers were more than happy to help and teach. Now those youth bowlers that came out bragging, just inspired the others to beat the tar out of them.
While there are classless bowlers out there, if you show the respect, you'll be treated much better, make more friends, and enjoy it a hell of a lot more.
