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

I'd also stick to the 15...the portion that is the alternate to 215 flows through some less densely populated areas. I like to go that route mid late morning to early afternoon on weekday. As posted, the 215 has stinkier transitions and some construction.

Check out sigalert.com (traffic map) on other mid week days to see how the route flows.