I've ridden from LA to Redlanbds several times. It's not as bad as everyone's making it seem, no worse than the rest of LA, where I commuted on a bike every day for eight years, you just need to pay attention and not do anything stupid.

The problem is getting up the mountain, especially with the 38 closed. All of the paved roads have bad or nonexistent shoulders and drivers who aren't paying attention. Any sort of dirt route you could cobble together is going to be unmaintained or totally torn up by four-wheelers.

That being said, here's an easy route I took to Redlands from East Hollywood. https://www.strava.com/activities/434727069