On the way back from Joshua Tree we stopped at Hadleys for date shakes. The sign in the store is right -- they are delicious and incredible.
I'm a big date shake fan. Over the years, I've had date shakes from lots of places -- the Orange Inn in Laguna Beach, Shake Shack at Crystal Cove, Indio Date Festival, and the old Santa Claus Lane in Carpinteria. Mother's Market in Costa Mesa makes date shakes and I had a very good date shake at the Summit Inn just over the Cajon Pass. Hadleys used to have a store in Carlsbad where you could get them, but the store closed. There's a place in Santa Monica that makes date shakes. I can find it, but don't remember their name. There may be a few other places.
The best date shakes are blended with vanilla ice cream and chunks of dates. Sprinkling cinnamon and nutmeg on top makes them even better.