There are definitely a good share of like-minded mammas here, especially in certain neighborhoods. My family tends to stick to the city proper and adjacent suburbs, we currently live in Wauwatosa. Maybe not as crunchy as some other areas, but the schools are good. Shorewood is another city that might be attractive to you. If you really want to live in the city itself, the area in Milwaukee called Bayview is uber-crunchy/alternative/hipster/whatever you want to call it. The regular schools are decent I think (someone who lives there would know better). There is a Waldorf school on the East side and the public schools do have a couple of Montessori schools. Again, since I don't live in the city, I don't have direct experience with them, perhaps someone else here does. (Each of these cities/areas has a branch of our great local natural foods co-op now that I think about it!)
In the not-at-all crunchy suburb of Menomonee Falls is the Well-Rounded Maternity Center. They have classes, mom's groups, etc that might help you meet people depending on how old your kids are and whatnot. (My son was born there, it's a free-standing birth center run by a doula and "staffed" by homebirth midwives. It's awesome.)
I hear there is an AP group around, although since I work I never can meet with them, I think they meet during the week. I want to say they are on Yahoo groups...
And I'll be your friend.
If you have any other questions, feel free to let me know! We really do love it here. The winters can get long, but we make up for it in the summer!