MrsFix, I live in Rockford and I've been looking for an alley nearby. There is a clown guild in the southwest subburbs. They meet in Chicago Ridge which may be a bit far south for you, but I can shoot you more information.
I wasn't able to attend this month's meeting nor will I be able to next month, but hopefully August!
Also
http://www.coai.org lists an alley in Grayslake. I didn't get an email response from them, but you could try calling the number and see if they still are around.