Welcome aboard Aguilar and family!
Was transplanted to Southern California many years ago, and camped just about everywhere. Although the Jeep and tent didn't have those pesky length restrictions...ha!
Have you checked out the Anza Borrego Desert State Park? It has a nice cross section of dry camping, RV Parks to RV Resorts scattered about. All depends upon your power needs.
Then there is Calico Ghost Town just outside Barstow. Our kids, and grandkids have all enjoyed this one.
And don't get too worried. Not EVERYTHING at the Colorado River needs a membership. We've vegged out at various Blythe campgrounds a couple times, just fishing and birdwatching.
Recommend you pick up the latest edition of Trailer Life RV Parks and Campgrounds Directory. It's far from perfect, but a great starting point. THEN you can triangulate with this website for real people feedback.
. We tried looking at a few RV campsites and found they require a membership. I found one in Lytle Creek that doesn't but they have a maximum RV length of 25' (my suburban is 25' long; 
seriously?). We don't mind paying by the night and would like somewhere by the water (lake, river, creek, etc.), not too dirty(swim-able), fishing would be nice too, 
and we have 6 children between 14 years and 19months old (good kids) 
. Any suggestions? We are looking for places mostly in S.California for either one day trips or just short of a week. we live 2 blocks from the Joshua Tree National Park and I would prefer to be at most 4 hours from home since we are just starting off. Baby steps...Thanks to everyone in advance.
