Rob:
Train is 6 hour ride to the Loop (basically same time as driving) and I think there are about 3 daily. Price is about $40-80 one way depending upon time and availability. It's OK if you're alone, but if you're traveling with someone, it's actually better to have a vehicle. City parking is "interesting" but you're not constrained by the El, but there's a TON of stuff around the El routes so it's not as bad as it sounds. I lived there for 3 years and my daughter goes to school there, so I've done both recently.
I'd drive to Rosemont and than take the El into the city for some nightlife. Any kind of music, any kind of food, anytime. Chicago is a GREAT city for a good time; it absolutely trounces Detroit on so many levels.
Hope this is still on, but the links are all dead.