California Code, Civil Code - CIV § 713

(a) Notwithstanding any provision of any ordinance, an owner of real property or his or her agent may display or have displayed on the owner's real property, and on real property owned by others with their consent, signs which are reasonably located, in plain view of the public, are of reasonable dimensions and design, and do not adversely affect public safety, including traffic safety, as determined by the city, county, or city and county, advertising the following:

(b) Nothing in this section limits any authority which a person or local governmental entity may have to limit or regulate the display or placement of a sign on a private or public right-of-way.