Shopping's great! South Coast Plaza and Fashion Island have lots of great stares and places to eat--and whatever they don't have, LA for sure has.
The only place I have ever been victim to racism is at the Wal-Mart in Brea... an ignorant White gentleman and his wife assumed I didn't know English and talked some smack, but I hurled a few choice English words at them and continued doing so as I followed them outside the store for a bit and they shut up pretty quickly. I would've followed them all the way to their car if I didn't have to push my nephew in the shopping cart.
That's really the only time. While I worked at Rubio's (a Mexican fast food chain), I was asked almost daily what my nationality was--to which I replied American, or where I was born--to which I replied Torrance, CA, or what I was--to which I usually just looked at them funny because I don't consider myself a "what." Heh. I'm mixed, though, so I know I'm difficult to categorize--and us Americans just have a thing for being able to categorize each other, particularly when it comes to race... which is hard to do with mixed-race folks (and lots of other folks, too). ^_^
On the whole, people in Southern California are nice and open-minded, I think. You run into some turds here, sure, but it's really a great atmosphere here... laid back, medium-paced (except for the 85 mph 55 freeway), and friendly. It's good for families and for business--Irvine, Costa Mesa, and Santa Ana have plenty of jobs to offer educated/skilled workers. Check monster.com to get an idea of what's available.
I work at the University of California, Irvine and the benefits at public institutions are great--although, with budget cuts coming (aren't they always looming here in CA), I don't know how it will affect hiring at schools. You might check to see if your wife's accounting certification aligns with any American certifications (or if ACCA's internationally recognized, just ignore me--I'm not well-versed at all in accounting), to see if your wife will qualify for higher paid positions.
I don't recall if you mentioned children, but whether or not you have any munchkins, you should research the school districts in your desired areas before you purchase real estate anyway--Irvine has some great schools, and Troy High School in Fullerton is one of the best public schools in Southern California... there are some threads on the forums dedicated to OC schools, so some of your work may be done for you on here already.
In any case, there is plenty of diversity among OC residents--and while some of us do stick to our own kind, many of us also love to branch out and enjoy meeting new people and making friends. ^_^