One of my favorite places where you can eat alone and have great food at a reasonable price is Yoshi's on Halsted St. Several people are usually eating at the bar, which is not isolated from the restaurant.

http://metromix.chicagotribune.com/d..._lakeview_heds

On the other hand, Chicago has a lot of Flyertalkers and a lot of Flyertalkers coming through. If you don't want to eat alone, I would suggest posting something in the Community forum. Often you can get a dining partner or several who would be happy to join you.