I spent a large portion of my fly fishing career on valley, I am sure some of the members can vouch for me from back in the day when I was still in the area. I have hiked/fished almost from valley forge to downingtown. I caught 1 brook trout down in what I believe is west valley. They are in there, but low numbers. This was around 2012-13 I believe. There is also a very small spring stream down near west Chester that has brookies. I can also tell you hiking back into the woods and throwing some streamers into some of those deep pools on valley you find will yield some monster browns. I’ve seen some monsters back there. Even in the park I’ve caught some 16”+ browns. But your either fishing streamers or micro fishing and loosing a fair amount of flies.