Isn't there a recipe using survival skill to purify water? I think it may be bugged though....can not remember because I have never used it.

I just checked out the area around lake mead:
the west shore is very short with 3-8 lurks depending on level and a ranger station, not much else, doesn't feel to home-y though.
the north shore has camp golf, but north of there are a couple patches of flat land and some bighorner.
the east shores are the worst: many lurks usually in groups of 2, many packs of cazadores in groups of about 5; Callville Bay didn't look so bad, aside from a cazador nursery (easily cleared with annabelle) the boat ramp looks like a good place for a tent.

As for camp guardian: I see no good place to set up a tent, no good flat land and the area consists of coyotes, scorpions of varying size, gint rats and gouls, as well as lurks in the caves.

The river-shores are a smarter choice though I've not reconed the whole expance.

Also, does anyone know how to change irradiated water to clean in the geck? That park location would be perfect without the water radiation..

There is, but it's insane. 30 dirty water, surgical tube, rad away, glass pitcher, and I think one other item.

Note: The following assumes you know how to use the GECK at a reasonable level.

Load up the cell that is Spring Mt. Ranch State Park, either that exact cell or Wilderness (-19,11). Open World -> Cells, in the middle of the window that appears is a setting for Water with a drop down box full of choices. Pick something else, such as one of the Purified or Clean water choices. Save as a new esp mod file, load in data files and you should be all set.