“The OC” is the New “Frisco”
I have never heard anyone from Orange County ever refer to it as “The OC.” I think it is much like when I lived in San Francisco and someone would call it “Frisco.” That person would be instantly marked as a poser and passed over at any social function.
Aside from French Canadian tourists and a few misguided writers on “Daybreak OC,” I have never heard the phrase uttered anywhere within county limits.