Being that your opening comment started with "Monument", tells me you've been around awhile (I keep calling it that too). Northern campgrounds are nice, not much water as you've been told. Going early in the year means less traffic, yes, but with those elevations, much cooler. In July/August (worst heat) it'll generally be 15 to 20 degrees F cooler than 29 Palms or the other places at lower elevations. I've camped near "Skull Rock" in August & day time temps didn't make it to 90F.

You're idea of a base camp vehicle is smart in my book, just keep it stocked with water & other supplies. As far as sport drink or water? Do both. Many riders will tell you, myself included, to mix or water down sports drinks 50-50. They go down much easier this way.

I'd stay on the roads too & be ready for goatheads. Those little thorns are quite mean!

For those readers that may be wondering why a guy from Wisconsin might have been camping in Joshua Tree National "Park", I was stationed at the Marine Corps Air Ground Combat Center in 29 Palms for 4 years in the '80s.