East of the railroad tracks. You can still camp out there, as long as you are one mile east of the tracks, unless you have a dune permit. You must camp within 50'ft of an authorized route, can only take an OHV on an authorized route or within the "navigable" portions of washes, and you can not access the dunes, unless you push the OHV over the tracks, or tow it with a street legal vehicle (CA street legal)... So... if you want to dune, get a permit and hit the washes. With the improved road, you can easily get down to the 20's, and should be fine pulling off from the road 100 feet or so, more in some spots. Past wash 20, you'll have issues clearing the angles in the washes.
If you aren't fixed to the north dunes, look at the Ogilby Flats or Dunes Vista area, between Ogilby Road on the east, I8 on the South, and the Railroad crossing/Sidewinder Road to the north. Its all hard pack, easy highway access, less folks on the big weekends, and can be good rides to the dunes from the east side.
