There's an excellent book for southern California:
A Birder's Guide to Southern California, by Brad Schram, published by the American Birding Association (334 pp; $23.95 when I bought mine). For such a brief trip it may tell you much more than you wish to know, but it's by far the most comprehensive source. Of particular help to you, it has suggested itineraries for birding-oriented driving tours, and it has lists of where to find regional specialties.
In addition, the local Audubon Society chapters have on-line resources. You might even find a birding companion to help you find your way around. I grew up in L.A. and San Diego, and I have no trouble driving around, but L.A., in particular, is vast, and it can be overwhelming to a first-time visitor. Go to
www.audubon.org for a list of chapters. In particular, check into the Los Angeles Audubon Society.
I also suggest that you also contact the Automobile Club of Southern California (
www.acsc.org) for detailed road maps. They have maps of most cities, individual maps of the counties (which are vastly larger than British counties), regional maps (e.g "Los Angeles and Vicinity"), etc. Contact me off-forum if you have trouble getting maps from them or deciding which to get.
For general bird guides (i.e. books),
Peterson Field Guides: Western Birds by the late Roger Tory Peterson (published by Houghton-Mifflin) is probably the easiest to use, but it's sliding out of date (and maybe out of print!). There have been some splits and lumps since publication of the last edition (1990). Kenn Kaufman's
Field Guide to Birds of North America (also published by Houghton-Mifflin) is also very easy to use. It's the guide I carry with me in the field. Peterson's uses paintings for illustrations, Kaufman's uses digitally doctored photographs, which are uglier (IMHO) but which work very well. It's the basic guide I carry with me. Recent taxonomic changes and range-map revisions have been slip-streamed into the latest printing. Some American birders here will probably recommend
The Sibley Field Guide to Birds of Western North America by David Allen Sibley, or even the continent-wide
Sibley Guide to Birds (both published by Knopf). They are superb, with by far the best treatment of hummingbirds of the general birding guides. But I think the Sibley guides work better for someone who is already generally familiar with American birds and who wants to zero in on two or three known possibilities for study and comparison. Experienced American birders also like the
National Geographic Field Guide to Birds of North America (no author -- it was assembled by a committee). I'm not quite so keen on it; some of the hummingbird paintings are laughable, for example. But birders far better than me carry it and even use it as a text for birding classes. Both Sibley and NGS use paintings for illustrations.
There are many great birding spots in SoCal, and even a visit to a city park or cemetery will net many new birds for you, in addition to reminders of home such as House Sparrows, European Starlings and Rock Pigeons. Habitats in SoCal range from sandy beaches to tidal estuaries to chaparral-covered hills to oak woodland to high mountain coniferous forests to sub-sea level deserts. But I think most will agree that one particular must-visit place is the Salton Sea, particularly the south end.
Katy Penland is probably better equipped to help you with Arizona. Don't know if anyone from Las Vegas visits this forum or not.