The concept and history of the valley is very cool, and the scenery is pretty neat. However, it's not the best marked for part of the stretch and I got a bit lost. For reference, I've hiked San Gorgonio and Mt. Baldy (up the ski hut way - very easy to get lost).
It's just over a mile, and very easy. I would recommend it if you have the time, but definitely falls into the "could miss" it category if you are on a tight schedule or aren't a fan of shorter nature walks. Real hikers will likely be disappointed - head to Lost Horse Mine.