Although the dry campus policy is strictly adhered to by the university, most students get away with it a time or two. Loud, obnoxious parties off campus get busted up pretty quickly, so trust your judgment and leave before things get too crazy.
Campus police have a good reputation for being understanding. At times they can even turn a blind eye, particularly to Greeks partying off campus. The best way to stay out of trouble is to be respectful to police and always have a ride home pre-arranged.