North Campground was pretty basic (and cheap) when we stayed there (August 2011) in a reserved site. Loop A is close to the Visitor Center and I think just about all the sites were pull through, no hookups. Coin showers were a drive away down at the general store. Other than the woods, it didn't have a lot going for it.
I usually like staying inside the NPs but I'd probably go with Ruby's next time.
Late August was pleasantly cooler (than Zion, Arches, etc) at the higher elevation but not cold, so July will probably be similar.