Welcome to California OCDO! Since you're new here... Check out www.californiaopencarry.org for information regarding California Penal Codes, Pamphlets, "how-to's" and fliers.
To answer your question... The racially-motivated Mulford act in 1967 brought forth PC ┬ž12031, which prohibited loaded firearms in public places (namely incorporated cities). If you do plan on open carrying, it is very well possible that you will be stopped and a 12031 (e) check performed on your firearm to ensure your compliance with the law.
Simply put, we don't have Loaded Open Carry as a majority of the other states do. At least, not yet. Once CA has incorporation of the 2nd Amendment again, CalGuns will be working on a rights-restoration campaign in the courts.