For what it's worth, I was at Knott's on Sunday just after the case had been announced in Orange County (coincidentally, more people were talking about Kobe's death than the virus). I did see a few more people wearing face masks than usual, but otherwise, no one seemed really all that panicked. It was less crowded than usual, but I'm not sure if it was because of the illness, the helicopter crash, or just that it's not typically packed in January.
I've read that so far, according to some experts, the new illness is mostly affecting people over the age of 40 and the immunocompromised. If you're generally healthy, it looks like you might be not necessarily safe, but even if you get it, it wouldn't hit you as hard. So if anyone is questioning whether they should go to Orange County, it's really not some crazy thing, yet at least. Bring a mask if you feel it would help, but I think you're likely to be okay.