I'm a 51 year resident of San Diego, and San Diego doesn't have any local laws regarding folding knives. Both San Diego county and city follow state knife laws.
As for California state law, the fact that a folder can be wrist flicked open does not make it illegal to carry, as long as the knife is designed to be opened by pressure applied to the blade using a thumb stud, thumb disc, opening hole, flipper spur, etc, and as long as it has a detent or other mechanism that creates a bias towards the closed position that prevents the blade from moving out of the handle under it's own weight.
Here is the specific statute in the California penal code that describes what I am referring to. This is a link to the official California state legislative website-
https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?sectionNum=17235.&lawCode=PEN
Prosecutors in California used to charge and prosecute people for possession of "switchblades" (gravity knives) if their folder could be wrist flicked open, but in 2003 the California Supreme Court ruled that knives with features I've described here do not qualify as "switchblades", and the penal code statute that I linked was changed to include language regarding thumb studs, detents, etc, directly from the courts ruling .