I'm thinking of hiring a 172 from Long Beach in August and taking a couple of friends for a flight to Vegas, over the Hoover dam and to see a bit of the Grand Canyon, but the question I have is whether I'm being a bit optimistic to have three in a 172 flying around those kinds of places at that time of year?
Dodgey with 3 people unless you load half fuel I reckon. You'll be ok out of Long beach and Vegas but make sure you do the performance calculations very carefully if you use a shorter runway and don't even try Big Bear or other high alt airport. it was 35-40C in most of the desert last week and even with 2 of us on a DA40 (180) we were a bit concerned. Unnescessarily as it turned out as performance was fine, the only problem we had was engine cooling in the climbs to 8500/9500 - oil temp started to get a bit warm at one point and we had to stop the climb.
Turbulence was a killer though, I'd steer clear of the desert anytime after about 10am or go at 11500/12500'.