Hello ktbb,
There is a sewing guild in Hillsboro - a quilt shop in Rochester (Peace and Applique) - a guild in Springfield - a shop in Ramsey - a guild in Carlinville (Macoupin Prairie Quilter's Guild) and check out
http://www.quiltguilds.com/illinois.htm - by locating local shops they can help you find a guild. If you have a chance the Macoupin County Fair is the July 19-24 and they will have a display of quilts along with the regular county fair events. If you have never been to a county fair, it is very interesting. The State Fair will be in Springfield in August. It is an interesting event also.
Good luck and hope you enjoy IL while you are here.