Camps can get expensive, but we found them a good vehicle for getting a more "up close and personal" look at the coaches, the facilities, the campuses and the culture of the programs during the junior year fall, so that we could figure out what schools we wanted to target. We went to camps only at schools that met son's academic AND baseball goals.
Many camps promise that you'll get a written evaluation. If they make that promise, don't leave the camp without it in hand. If they don't promise one, then an e-mail expressing interest in the camp but asking if an evaluation will be provided is entirely proper. Because they want you and your money to come to the camp, they will likely cooperate with a polite request.
When you are standing on their soil, they can talk to you for as long as they are interested in talking to you. If they talk a lot, that indicates interest. If they seem in a hurry to move on, that can also be meaningful. Especially if they've already seen you in action at that point (hitting, fielding, pitching or whatever).
The key thing is to determine what schools interest YOU. Then be proactive. Try to elicit interest from the schools you want. You're a year away from your NLI signing period. You have time to shoot for exactly what YOU want right now. If for some reason those schools don't seem interested, there's plenty of time to adopt a fall back plan -- seeing if anyone's interested at all -- much later on.
I don't see any point in going to paid camps at schools you don't care about. Choose just a few, if even that.
If your son starts getting invited to "junior days" over the winter, great. If his whole junior season passes without anyone seeming all that interested, then maybe that will be the time to broaden the search and try to get more people to look at him over next summer.