Is it illegal to simply be naked in public in San Francisco?
Generally, yes. A person may not “expose his or her genitals, perineum, or anal region on any public street, sidewalk, street median, parklet, plaza, or public right-of-way.”1SF Police Code Sec 154
Except this does not apply to “any permitted parade, fair, or festival held under a City or other government issued permit.”
But even during such festivals, it is illegal to be naked in public restaurants or public seating areas:2SF Police Code Sec 1071.1
(a) Waiters, Waitresses, and Entertainers. Every person is guilty of a misdemeanor who, while acting as a waiter, waitress or entertainer in an establishment which serves food, beverages, or food and beverages, including but not limited to, alcoholic beverages; (1) exposes his or her genitals, pubic hair, buttocks, natal cleft, perineum, anal region or pubic hair region; or (2) exposes or employs any device, costume or cover which gives the appearance of or simulates the genitals, pubic hair, buttocks, natal cleft, perineum, anal region or pubic hair region; or (3) exposes any portion of the female breast at or below the areola thereof; or (4) employs any device or covering which is intended to simulate such portion of the breast.
(b) Members of the Public in Restaurants and on Public Seating. Except as provided herein, every person is guilty of an infraction who, (1) while present as a customer in the public eating and drinking areas of an establishment whose primary business is to serve food, exposes his or her genitals, buttocks, or anal region; or (2) sits on any public bench, public steps, or other public seating area without clothing or other separate material as a barrier between his or her genitals, buttocks, or anal region and the public seating. Any person who violates this Section 1071.1(b) shall be deemed guilty of an infraction and upon conviction thereof such person shall be punished by a fine not to exceed one hundred dollars ($100) for a first violation, and not to exceed two hundred dollars ($200) for a second violation of this Section 1071.1(b) within a twelve-month period. Upon the third or subsequent conviction within a twelve-month period, such person shall be deemed guilty of a misdemeanor and shall be punished by a fine not to exceed $1,000 or by imprisonment in the County Jail for a period not to exceed one year or by both such fine and imprisonment. This Section 1071.1(b) shall not apply to children under the age of sixteen years.