The Rockford USABDA chapter hosts dances every 4th Saturday of the month at the Community Building in Belvidere. The dances start with an hour-long beginner level lesson, and then general dancing begins using taped music. The evening is interspersed with some foxtrot mixers, and there is usually a dance demo.
There is also a 2nd Friday dance at Memorial Hall in Rockford, again hosted by USABDA - I think they keep a summer schedule there, but I'm not completely sure.
Check out the Rockford USABDA's website at www.danceframe.com They post the monthly newsletter on the site, and they give information about other places to dance in the Rockford area, too.
Have a good time trying them out!