I wouldn't worry about that at all as long as you trust your kid. I was 20 and a junior when I was on my DCP. It's true that it basically is just like college, if you don't get involved with those things or people then you won't have any problems. Under 21 you have to live in wellness and you can get termed if anyone has alcohol in the apartments.
Basically, you'll get to know who the party people are on the fb page and you most likely won't see them unless you actively seek them out. I lived in Patterson with 5 girls. All but 1 was under 21 and they respected the rules of no alcohol in the house. Two were random roommates from Australia who did love to go to parties, but they were extremely mature and never brought boys or anything else home. As others have said, I found all (2 random weren't in the plans) my roommates on FB, you can fill out surveys whether you drink, when you sleep, how you clean, etc. It's pretty easy to find similar people.
I never saw cops or security or anyone while on my CP or at Patterson. Didn't have any problems with roommates or people next door, it was a quiet place. FWIW I absolutely loved my program and my roommates, I'm moving back in with some old friends from there after graduation.