I'm not very knowledgeable on Caldwell, I've only fished it once, but between it and Sandy I'd pick Caldwell. Last fall and this fall it got stocked with fingerlings, and from what I understand it is also half decent for wild fish(though they're not easy). There could be a few adult stockies left from the spring, not sure. The west branch may be worth a try for wild fish also.
Sandy gets warm in the summer, so I doubt very many if any trout are left from the spring. Little Sandy is another option. It has fingerling stocked fish, adult stockies(as of Sept there were a few left from the spring stockings), and wild fish.
Seeing where you're from, the Erie tribs have a good abundance of fish this time of year ;-) Oil's another option. And if you want to keep driving south on 79 you have Neshannock..