I was in that area for a "regional" rally put on by the Motorcycle Sport Touring Association. The MSTA is non-brand specific with no displacement requirements (personally, I've gone to rallies on everything from a GL1200 to a CB300F and lots of in-between including my NC750X) and is full of enthusiastic folks who like to ride. We don't do parade rides (a "big" group for us is 4-6 bikes), and we had about 50-60 bikes at Spring Green from all over. Street routes are provided (and sometimes adventure routes) for riders who may not be familiar with the area, but you can ride as much or as little anywhere you want. We have weekend rallies spread throughout the year in locations ranging from Colorado to Wisconsin to Arkansas to Georgia. If there are curves, we go there.
We had our national rally up in LaCrosse a few years ago, and I've attached a BaseCamp screenshot of some of the routes we used then and in Spring Green. LaCrosse is located in the extreme upper left hand corner of the screenshot with Madison in the far lower righthand corner for reference.
I'd be happy to have suggestions from a local person...more options are always better. I may very well be headed back up that way next summer.