I'd definately recommend getting out and seeing some sights. Going to Frankfurt is super easy (station is in the basement). Trains depart every 15 minues or so and it only takes about 10 minutes to get to the Hauptbahnhof (Main train station). Take the U5 to Dom/Römer for the tourist stuff (pretty reconstructed half timber houses). There is a tourist information office in the train station and at the Römer. If you're there on a weekend, check out the Ebbelwei express, a fun tram which takes you through the city.
http://www.ebbelwei-express.com/html/index_e.html
Otherwise, Mainz is also very nice. The old town and cathedral (1000 years old!) are nicer than Frankfurt. Mainz is somewhat farther away (25 minutes or so), but also somewhat more attractive IMHO. Strolling along the river watching the boat traffic is a pleasant diversion.