I concur you should fly LAS-LAX. The traffic can be terrible, especially on Sunday. PHX-LAS passes through a Joshua Tree "forest", lots of pretty desert mountain scenery, and of course goes right by Hoover Dam. There's not much to recommend on the LA-PHX drive; Hadley Fruit Orchards in Cabazon is a good place to take a break and get a date shake. If you happen to pass through Quartzite, AZ in February during the big rockhound festival it is quite the spectacle-RVs as far as the eye can see, sort of a senior citizen Burning Man.