We stayed on that road a few years ago. Didn't sign in with anyone - was there at the spot we chose for nearly a week and saw no one but our neighbors. It may have changed - not sure.

Quartzsite is the only place I have seen a sign-in on BLM land.

No sign-in is necessary 👍

You do not need to sign in, just be aware of the time limit. We were there for about a week and did not see a ranger come through.