The belt carry refers to fixed blade knives. Pocketed folding knives are fine, with the limits noted above for assisted, vs switchblade, etc. The laws are a little obscure but can be looked up.
"Pursuant to California Penal Code section 25610, a United States citizen over 18 years of age who is not prohibited from firearm possession, and who resides or is temporarily in California, may transport by motor vehicle any handgun provided it is unloaded and locked in the vehicle’s trunk or in a locked container. Furthermore, the handgun must be carried directly to or from any motor vehicle for any lawful purpose and, while being carried must be contained within a locked container.
Pursuant to California Penal Code section 16850, the term "locked container" means a secure container that is fully enclosed and locked by a padlock, key lock, combination lock, or similar locking device. This includes the trunk of a motor vehicle, but does not include the utility or glove compartment." FWIW, the "utility compartment" has not been more fully described/defined. I suppose one could put a locked container in the glove compartment but that's perhaps asking for trouble?
They don't really mean "any" handgun. It's any handgun that is not considered an assault weapon. As a visitor or potentially new resident, you could not legally import an assault weapon. The most likely gotcha is the threaded barrel and/or magazine capacity. The California AW definitions are in the stickied threads at the top.