The best advice is that the parties and bars get better as you get older. Students learn to throw better parties and where to go out at night. Philly's public transportation system is really good; the toughest part is figuring out which buses, trains, and trolleys go where. There is a subway, but it mostly runs toward South Philly, which is nowhere near St. Joe's. Students who make the best use of public transportation generally are the best partiers because there's a lot of very fun bars to discover that aren't proximal to St. Joe's.
There really isn't a lot to do for kids younger than 21 outside of house parties. Clubs such as Shampoo offer alternatives during the week, but most clubs and bars become extra tight on the weekends. There are a couple of good places in the city to catch concerts, shows, or festivals, but by the time most St. Joe's kids find out about these venues, they're not younger than 21 anymore. Drexel Arms Apartments is mostly dominated by frats and sororities, but it's not your typical frat scene, and most people won't be turned off by it. The only real significance is that those in the Greek organization having the party won't have to pay to get in while others will.