I live in San Diego where the knife laws are pretty lenient, but periodically go into (and rarely, have stayed awhile) in LA. I have never had a problem with whatever I was carrying. If I were really worried about the City of LA, I'd carry one of my 3"-bladed Spydercos, like my Narive 5 or Delica. But like I said, I've never even come close to having a problem with 4"-bladed folders. Sure, the City of LA might not be the greatest place for knife carry, but it sure ain't NYC, Boston, Chicago, or some of the other places in this country with their totally ridiculous knife restrictions. In the City of LA, if it's a larger folder, you might not want its pocket clip showing, but that's about it. I don't know about neck knives.
Jim