Pretty much any wooded lot would do. Just make a few portable flag stands, go out in the woods and get on it. Or if you have a friendly field who has a woods field with some decent bunkers and will allow you to put up temporary flags, that would work well, too. Most important thing to work on is communication across a large area, and you don't need anything special for that. We played UWL and SPPL before that for about 5 years before any other Chicago teams started playing 10-man woodsball, and that's how we did it.
I can't think of any WI UWL teams off the top of my head, so finding a practice partner will be a bigger challenge.
One final word of advice: Move faster.