hi,
we did a similar trip for our honeymoon, hired a car for the week.
Starting with 2 nights in San Fransisco ( didn't use the car much, parking can be a nightmare)
Drove down the coast road overnighting at santa barbara ( nice but expensive),
Then LA for a night (wan't that impressed, altough studied a nice veyron on Rodeo drive) & three nights in vegas. (Red rock and grand canyons are impressive, just like the westerns,
But the grand canyon's a long drive)
Driving was easy, as Thomo says, get a good sat nav ( remember to change states) also remember you pay for your fuel before you pump first in most places .
Hiring a fairly large 4 x 4 was around £500 for the week.
hope this helps