What the hell is going on near the Homestead Trail and Cross Hike in Palm Desert?

Tipster Donna sent us this photo and, well, perhaps someone is making Palm Desert great again?

Palm Desert Wall at the Cross Hike
(Donna Ernst)

So what is going on?  Is Mexico paying for this?  Or is this all just some sort of promotion for that dumb looking Matt Damon movie coming out?

Please offer up your theories in the comments.