I lived in Coudersport for a year, right across from Mill Creek. That was like 2003, though, so things may have changed some. Then again, I doubt they changed much...
Mill Creek is class A browns, and fairly well known to carry a few big ones. The downside is that it's pretty thick and difficult to fish, and not always the most attractive of settings (given that your in Potter County and all). But so long as you are aware of that, it's a worthwhile piece of water.
The Allegheny also runs right through town, but it's channelized in town. There are wild fish above and below the channel, in addition to stockies. Just below the channel (first 2 pools) can be accessed just below the bridge in town there. It's been a few years, but it was a grocery store lot I parked in, there's a dollar general or something there as well. That area is probably 75% stocked fish and 25% wild browns. As you go down from there, the % of wild fish declines and it's getting on the warm side for July. Still, it's well known to hold a few wild browns, which tend to be big, and it's a popular night fishing area. All the way to Roulette (by which point is pretty much a straight warmwater fishery).
As you go upstream from town, it's still stocked, and the farther you go up the more wild fish you run into. There is a special reg section up there. If you get up high enough it transitions to brookies.
As far as other options, well, it's Potter County, there's more than you can shake a stick at. While there's a few streams north of 6 (Oswayo and the upper Allegheny, for example), the prime trout area in the county lies to the south of 6. There's the First Fork/East Fork drainages to south and upper Pine Creek and W. Branch Pine Creek to the southeast. The Upper Kettle drainage pokes in between. Pretty much all of the streams have wild fish (browns or brooks or both), but generally, the bigger the water the fewer % of wild fish (but higher likelihood of stockies).
Fairly popular ones within easy striking distance of town include Lyman Run (upstream of the lake). One I liked when I was up there for a quick hitter was Freeman Run (flows through the broken Austin dam). It's best around the dam and just upstream, but if you go too far up a lot was posted. I'd catch maybe 50% wild browns, 25% wild brookies, and 25% stockers.
As far as water levels, if the rain is now done (I dunno if it is), I'd expect the big waters to still be up, but some of the smaller waters should be in decent shape by the middle of the weekend. Go to the upper Kettle or East Fork drainages and fish tribs.
