In central California in modern times I have had no trouble whatsoever carrying fill lengths machetes on my belt, as well as full size antique bolo knives. I've had to interact with police on various occasions and I have never had any trouble. If anyone makes a mention of it at the grocery store or something I simply say that it's legal on the belt. The police have always agreed with me. In California any knife that is over 2 ½ of blade is supposed to be open carried, thus can be on your belt, on your neck in a sheaf, on your backpack, or on your shoulder like a samurai. Folding knives aren't supposed to open with a button, but the ones that have the rear nub that sticks out when closed, counts as part of the blade, so pressing on it to let the spring Open the knife is legal. And frankly you can get away with 3 inch folders in your pocket too. Just be careful that a knife you are wearing isn't concealed, like in a horizontal carry on the back of your belt. I usually carry a fixed blade there and it does get hidden by my coat, but when I have to deal with a cop I generally draw them with my back to him for a ways away where he can see, then drop them, then turn around and approach him to see how I can be of assistance. Sometimes they will pat to double check but not usually, I always carry 2 knifes. There are a lot of ways to strip a knife from someone if you know what your doing, but there has not yet been a method devised to disarm a knife from each hand without getting poked extensively. Except for shooting the person obviously. I do alot of knife throwing, and stuff like that, nothing too nefarious of course. But I have had to use a knife to prevent myself from being seriously harmed before. I'm happy to box someone's ears to settle a disagreement, but if 4 thugs try to get your wallet, a blade will change the game quite a bit sometimes. ( Yes I know your supposed to give the wallet and flee, but that would have resulted in marking myself as a prey animal and invited widespread problems. Sometimes teaching someone that your definitely not worth the effort is in fact the only way to go. I just can't punk out like that, I wouldn't be able to respect myself.)
Buy anyway, avoid double edged knifes, hidden knifes like sword canes And belt buckle knifes etc, no switchblades or butterflies, or push knives. Don't take them to government buildings like schools, dmv or courthouses. Hospital won't let them in but will store them for you at security desk on the way in. Otherwise your pretty much good. Ohh, no stinger knives either, you okay, the one that injects the wound cavity with compressed air through pores on the blande and a tank in the handle. Turns a knife wound into a shotgun blast. Hell of a thing.