i live in Costa Mesa. i ride almost everyday, as it's my only (motorized) form of transportation. i've never been stopped, and i ride my bike like it was a motorcycle. it's registered, and i have the plate on it. i've got a tailight, that actually works as a brake light, and that's it. the only time i ride at night is when i don't make it home in time.
i ride busy streets, like Newport Blvd, Harbor, 17th, etc, in traffic, at 40+mph. i use left turn lanes, pass cars and busses on the left, and pretty much follow the rules of the road, like a scooter. the only time i ride in bike lanes is if i can't keep up with traffic, since everyone speeds here.
i see at least 10-20 cops on a daily basis, and none of them have ever done anything, except for giving me a second look or something. i've been in front of them at stoplights, next to them at turn lanes, and yesterday i was drafting a box truck down Harbor where it goes under the 405, in the middle lane (because the right three lanes get on the freeway,) about 50mph, and there was a MC cop next to me the whole time. i think he was smiling...
i kinda like pushing my luck around cops. i'm waiting to get pulled over, just to see what they say.
i think one thing that helps me out, is my bike doesn't look like an unsafe "toy." i use Opti2 oil so it doesn't smoke, i've got the baffle in my exhaust, and my bike has more of an old-timey motorcycle look, instead of a thrift store death trap.
i think Orange County gets a bad rap, and i don't really know why. i've been hassled more times driving a car than on my bike.