The Campsites:
Boyd,
do I see Cindy and lightning's family in one of the san marcos pics?
Good eye Smitty! That is Cindy and Lightning's mother (facing front) and brother (facing rear) at San Marcos camp.
Boston Mangler is right that San Marcos is one of the best camps; you'll have to fight me for it!
I usually bring enough people down with me that we take almost all of the camps, so the privacy issue isn't so bad.
Castillo is an excellent spot for a large group of 4-10 people (hot tub + swimmin' tub)!
El Dorado is another good group spot. It has a huge palapa and 4-6 tents could easily fit underneath (with room to spare).
El Mirador is great for 1-2 couples and is very romantic.
El Sol is very nice for 2-6 people. Good spot for winter as the tub gets full sunshine almost all day.
La Paloma is another favorite. Very private, very shaded site for 2-8 people.
La Jolla has two spots, A and B which are best used together (too close to have strangers right there). These also tie in nicely with La Paloma for a mini group camp.
La Cueva is an overflow camp that we joke as being the armpit of Guadalupe. The tubs are so-so, but it is great for a group of 10-20 people who want to interact all the time. Also a great spot for higher temperatures because it is heavily shaded and tends to stay 10-15 degrees cooler than any of the others.
When I take groups down; we usually rent 4-5 camps and tend to keep our numbers at each camp lower. This lets you interact as a group when you want, but lets you have some privacy and romance as well. Plus most of my friends have dogs so we need the extra space.

One time we had more dogs than people on the last day!
Boyd