I stayed at the Essex Hotel when I ran the Chicago Marathon in 2000, it's right next door to a Radisson Hotel(I think)and is right across from Grant(?)park. We took a cab from the airport(don't fly into Midway, so my husband says--he's from Chicago), and it cost about 30 bucks(these are 6 years ago prices). Hubby said don't bother with a car, it's too expensive to park and FINDING parking can be a bear also. The Essex isn't the Ritz Carlton, but it was clean and for a place to sleep was just fine. They have a van service where every 30 minutes(or so, they had a schedule)they will take you down to Miracle Mile and drop you off and all we did was tip the driver 5 bucks(each) and told them when you wanted to be picked up(we tipped them on the way back also). My girlfriend(hubby couldn't make the trip, he had to work)went to the Museum of Art and LOVED it, said it was HUGE, AND, it's not far from the Essex hotel. Since I was doing the race I didn't do a whole lot of sight seeing, but we did do the Sears tower, it's a bit of a wait, but pretty cool--she did the sightseeing since she wasn't a runner. We went to Mike Ditka's for dinner, very nice.
She liked Chicago so much she wanted to move there, a very hip, yuppy feel--she wanted to ride the "L"(the elevated train transportation system) to which I said NO--
fine if you know where you're going, but not for the tourist in my opinion, I would go with my husband if we visit Chicago again, only because he's built like a football player(and he's a sheriff's deputy).
Just for hotel info you should be able to go to the Chicago Marathon website and get info, the race isn't until October, but they should have info about different hotels. Oh, there's also Navy pier that's along the shoreline, didn't get there but it looked like a lot of fun.
Hope this helps!
Mary