For the fine dining, you might consider Charlie Trotters. One of the best.
http://www.charlietrotters.com/restaurant/I'd grab some pizza. Lou mallinotti's (sp?) is classic.
There are some great little mexican places like La Pasadita (on Ashland, I think). Probably 20 minutes from downtown.
Pub grub at Goose Island brewpub is another good idea (near North and Clybourn)
Chicago Diner is a great vegetarian diner on the near north side.
Wishbone is great for breakfasts, quite reasonably priced, and they even have a loop location now.
I'm not sure where to get the classic chicago hot dog, because I don't eat that kind of thing, but it should be everywhere...
Hmmmmmmmm....there is some cool restaurant on the 95th floor (or something) of the John Hancock building. It has a nice restaurant and a lounge on the floor above. AMAZING view. Once just went up there for a beer (or was it for coffee). I'm sure a full meal would get pricey, but for a drink and maybe an appetizer it is well worth it.
http://www.signatureroom.com/ open til 12:30, or 1:30 on weekends, so pretty late night. Here's the lounge dining menu
http://www.signatureroom.com/Signature- ... ing-Menus/ ...It looks like they require one main course if you sit in the dining area (95th floor). But like I said, quite an experience to go to the lounge for a desert, appetizer, and/or a drink. And great downtown location.
Have fun!
Dr. Nimbus Couzin