If you like to ride bikes and have fun this is a good fall activity and very beginner friendly. Cross is fun to watch as well with many spectators choosing to taunt the riders as they go by and the ubiquitous beer hand up.
Not only is Wisconsin a lucky to have a long race season with tons of different courses, we also have many different teams so its easy to find friends to practice and race with. In Madison, consider joining Mad City Velo, Trek Midwest, Brazen Drop Outs, Magnus, or one of the other friendly teams. Milwaukee has a lot of people on the Team Wisconsin, IS Corp, Hampshire, and My Wife Inc. teams. There are additional teams across the state including the Big Ring Flyers in Hudson.
Not interested in racing but still looking to keep in shape for fall and have some fun rides. Join one of the various cross practices around the state. The biggest and best takes place at Badger Prairie in Verona on Wednesday nights beginning at 5:30 p.m. It is common for more seasoned racers to help teach the beginners new skills and techniques.