I think in most cases you are right as far as keeping hunting places quiet but I'm the exception. After 30 years of metal detecting there isn't much I haven't found. I would like to find a flying eagle cent but for the most part I get a bigger thrill watching some else recover a nice find.
My favorite places are Wright Park, St Marys, Fort Atkinson and Fort Dodge.
At Wright Park its pretty much a hit and missed since I cleaned out the easy stuff 10 years ago
but there is still plenty of good stuff left. All around the band shell can produce coins back to the 1800's as does the north side of the Hoover Pavilion.
At St Marys, since I pretty much cleaned out the south and west the north lot just north of the old main building is still producing. We found several silver quarters there this last weekend. The old field where the baseball diamond is north of the Sheridan Center is great for older coins but getting in there may be a problem.
Fort Atkinson always has the potential for really old finds but you can hunt for hours before finding it. Best producing area is midway down the road that takes you to the river. If you park your vehicle right near the marker walk west midway through the first field.
At Fort Dodge go to the field just east of the fort and stay along near the river bank. Most coins have been found at the southeast corner of that field, although we've found them in the middle as well.
If you'd like to go hunting keep an eye on this board and I'll let you know where we are going to be.