If you're up for the drive, there's a public range (yes, public!) in Shiocton. They have a "donation" box when you drive up and ask that you pay $3 so they can mow the lawns and whatnot, but that's all the fees you'll ever undertake.
There is no range supervision, no one telling you what to do. They have a dumpster in the parking lot, so feel free to bring anything (read: anything)
to shoot at, as long as you pick it up afterwards.
The people I've met there are always friendly, and occasionally you'll see some guys with .50 BMG's or machine guns, so that's always fun.
Anyways, its about 30 minutes NW of Appleton, so it may be too much drive for you. But since you requested an "open carry" friendly range, this one is friendly to anything. My friends and I keep our sidearms on our hips the whole time, and practice quick draw firing.
As a final note, I should add that there are 3 ranges there. There's a 500 yd, a 200 yd, and a... uhh, I believe its a 300 yd, but I've never been out to that one. The 500 yd and 200 yd are separated by a berm, and the other one is visible but you have to drive around a pond to get to it.
Best of luck to you!