Mauriposa is right, as usual! Late night on Mondays, Sidetrack is the place to be. It's the inspiration for my weekly BWW column, "The Showtune Mosh Pit!"
But you are right, POL. Those are the main musical shows that will be up when you are in town. There are a number of websites that do a good job at listing upcoming performances, but the League of Chicago Theatres has just revamped their website,
http://www.chicagoplays.com , and it is a great place to start looking for things. The League also runs Hot Tix, which is the half-price service we have (
http://www.hottix.org/index.aspx ). Check it out!
And I hope you have a great trip stateside, and to here in the Windy City!