Know What You're Getting Into – Most night-time events at Bryn Mawr involve dry parties, movie nights, roller rinks or art parties. The Bryn Mawr Concert Series brings underground groups to campus every few weeks, and those parties are pretty large but are mostly attended by Mawrters. The organization is working to garner outside interest.
I spend Friday and Saturday nights at Haverford with the friends I've made there. Bryn Mawr students who are into hard parties generally head over to Villanova or into Philly.
There are a bunch of dive bars in town that are fun if your expectations are low. If you're into dancing with your girlfriends by the jukebox, or into hosting your own party in the dorm, Bryn Mawr is a fine place for that kind of thing.