Thanks for the response. My main targets are Condor (I've already ear-marked Pinnacles NP), Roadrunner, Burrowing Owl & any Hummingbirds - but as I've only been birding in US once (a week in Florida), plus a couple of ski trips with incidental birding, a lot of western species will be new to me.
I've got a couple of days around Vegas, then four days to travel between each of the three cities and a couple of spare days around LA before leaving. So far I'm planning on visiting Grand Canyon, Yosemite, the Californian coast & Salton Sea and have checked Ebird hotspots but I'll be happy to hear of any other not to be missed locations.