Probably what you have seen is the Newmar owners "Gathering in the Desert", they haunt that area around that time of the year. This is just a bunch of owners getting together to socialize, attend the show and etc.. A lot of attendees will probably be affiliated in some sort or another with the Newmar Kountry Klub but believe it is just pull in, find a place to park, then join in as you see fit. They will be there this year from the 13th thru the 17th of Jan, here is a
link to the thread that talks about this winters event.
This year there will be an Official Newmar Kountry Klub rally in the pretty much same area, it will take place the 21st thru the 24th of Jan. This is a members only, fee based rally.
Spike