When I was doing a project in downtown Chicago, I took the opportunity to visit a few.

I don't know if it still holds true, but at the beginning of last year....

You can catch a free bus every evening from the big Hilton to Harrah's (Hammond, Indiana). The bus was on the half hour and the last one would leave at 11:30pm sharp... you miss it, your walking.

The Empress had stopped their service by this point. But you could also catch the bus from Chinatown to the Grand Victoria.

I would check with the Marriott Concierge desk (even if you are not staying there - its across from Disney Quest). They have a good handle on the different riverboats, and the schedules and where you sign up.

You could also catch a bus from the Chinatown