Coming from a guy who spent 4 years there, in places like Corcoran, Chino, & Lancaster, all California lockups. I can tell you that the Judge has ZERO influence on where you serve your time. That is all decided by the classification commitee which you see about 1-2 months in to your stay. They look at your classification score and determine where you'll fit in based on what beds are available in the various institutions.
In California, prison culture is racist to the extreme. Whites do not share food, cigarettes, etc.. with blacks. Whites & Mexicans can share things, but trust me, as soon as a fight breaks out, and it happens regularly, the races divide like Moses parting the Red Sea. Its sad really, its like getting in a time machine and arriving in 1960's Alabama. Thats how bad the racism is.
People in prison, in general, are pretty stupid. But not the affable stupid of a Forest Gump, more like the dangerous stupid of a violent person who is threatened by things that he doesn't understand, and being dumb, there is much he doesn't understand. For me, one of the biggest challenges was hiding all trace of emotion or reaction when someone would come up and say the most moronic backwards crap, usually about another race. You just have to let that kind of thing go.
#1 thing your son should do. Work out and start taking MMA classes. Being able to defend yourself or at least to appear imposing enough as to not be an easy mark is very important. I had a year headstart on my term, so I hit the gym hard and took lots of sparring. When I got there, most people left me alone, but even as smart as I played it, I had to fight a handful of times.
To the OP, if you want to PM me we can take this offline and I'd be happy to speak with you on the phone and answer any questions you might have.
Bottom line, the time will pass, and if your son plays it right, he can do a lot of growing up in there and come out the other side a better man. I did.