Loving all the great ideas here, but allow me to play devil's advocate for a sec, if you will.
I had similar issues when I lived in Michigan at the end of a private drive that had a turnaround. In addition to my lawn getting torn up by party-parkers, donut-dorks, racing-reprobates and the like, I also had to deal with these dill weeds bashing my mailbox and post.
I decided I would put an end to it once and for all, and started discussing with some friends what my plans were. First of all, I was going to do the Big Rocks thing along my property at the turnaround. And then I was going to mount my mailbox to a big pipe that was filled with concrete. Figured that would send a painful message to whoever decided to wield the bat next time around.
Come to find out, if anyone got injured by my protective measures, EVEN IF THEY WERE VANDALIZING OR DAMAGING MY PROPERTY, I would be held liable.
So I didn't do that.
Ultimately, my solution was to mount a fake camera with a sign pointing at the mailbox, sit at my turnaround with a camera and other such wastes of my time until that generation of kids grew up and moved away, and my reputation as being that "Scary woman at the end of the street. Don't piss her off, man." was totally solid.
After all that work -- decades of it -- I moved to Toledo. I don't have decades left to do all that again. Mess with my stuff and I will make you wish you hadn't been so stupid. Just sayin'...