San Diego City Nudity Law
San Diego, California, Municipal Code 56.53: Nudity on Public Lands:
c. NUDITY PROHIBITED. No person over the age of ten years shall be nude and exposed to public view in or on any public right of way, public park, public beach or waters adjacent thereto, or other public land, or in or on any private property open to public view from any public right of way, public beach, public park, or other public land.
This law applies to the section of Blacks Beach that is in the city, but not the portion in the state park.
San Diego County Nudity Law
SEC. 32.1004. PUBLIC NUDITY PROHIBITED:
It is hereby declared a public nuisance and unlawful for any person to appear, sunbathe, bathe, walk, disrobe, or otherwise be nude in any public place except in an area expressly set aside for such purpose or in those portions of a comfort location, if expressly set aside for such purpose. Any person who shall violate any of the provisions of this chapter shall be guilty of a misdemeanor and, upon conviction thereof, shall be punished by fine of not more than $500 or by imprisonment in the County Jail for a period of not more than six months, or by both fine and imprisonment.