I'm diggin' on all of the misinformation in this thread so far.

The County Class I bikeways are all officially closed this time of year at 6PM. There is also a 10MPH speed limit for bicycles on them. Neither seem to be enforced, but both should have been mentioned by those suggesting their use after dark.

As far as those who don't recommend riding the streets at night, they apparently don't have a very good grip on math. Fewer vehicles equals fewer chances of having an incident with them. I've ridden all over the county at night and am still here to talk about it (except Ortega Hwy, which is on my short-list to hit up).

To the OP; use good lights, your imagination and Google Maps. Using secondaries and resedential thoughways at night is great. Irvine has so many Class II bikeways, connecting up secondaries and resedentials is super easy. Accessing Anaheim Hills and Yorba Linda from Irvine is easily possible with these tactics in mind.