I don't carry and I'm not a lawyer, but for what it's worth, according to the LA County and LA City ordinances, open carry is only prohibited for knives with blades over 3 inches. So, it's not explicitly stated, but it would seem that you could carry a sub 3 inch knife with or without the clip showing. Or, using similar logic, a 3+ inch folder, concealed.
It's been about a year since I moved from Southern to Northern Cal and I can't recall the last time I noticed seeing a knife clipped to someone's pocket there. So it might be prudent to carry without the clip showing, to blend in with everyone else, if you're feeling a little paranoid about it.
And under California, there's no blade length restriction for carrying a closed folding knife, concealed.
Here's a forum thread on LA knife laws.
Have a good trip!