San Diego to Las Vegas-Stay on 15 or use 215 to skirt LA?

I would take I-15. You are far enough away from LA that you won't be over whelmed with tfc. Travel in off hours.

I would just stay on the 15. To get to the 215 from the 15, you would have to take the 91 and that route goes right thru Riverside and San Bernardino.

Ron

We use 215 when in that area.

I would take the entire 215 end to end rather than take 15. You are right that it's about the same but there is usually much less traffic on 215 most any time of day. It's also a couple of miles shorter.