Or maybe they were doing something less "arty" at their place of work --I'm not sure.
From Asbury book on San Francisco's Underworld, Chapter Ten "Company, Girls!":
"The location of every brothel on the Barbary Coast, whether crib, cow-yard, or parlor house, was indicated at night by a red light which burned before its door from dusk to dawn, and during the day by a red shade behind at least one of the front windows. From some of the parlor houses also flapped signs, gaudily painted on wood or metal, which bore the name of the establishment and, sometimes, pertinent information about its inmates. Madame Gabrielle’s bagnio in Dupont Street (Grant Avenue), which she rebuilt in Commercial Street after the fire of 1906, displayed an ornate sign which depicted a huge insect lying at ease in a bed of fragrant flowers, surrounded by sweet-faced, simpering Cupids. Her place was called the Lively Flea. Near-by, another and an equally flamboyant sign ornamented the entrance of the Parisian Mansion, which was owned by Jerome Bassity and Madame Marcelle. Also on Commercial Street, during the first year or so of the present century, was a very popular French bawdy-house before which swung the cast-iron figure of a rooster, painted a brilliant scarlet and with a red light burning in its beak. The talons of the metal bird clutched a placard on which was painted the legend: “At the Sign of the Red Rooster.” In the hallway of this brothel was a smaller replica of the figure, and a sign similar to that outside except that it bore a shorter synonym for “rooster.” The Red Rooster was the property of Madame Lazarene, who also owned several other resorts, some of which were in the name of her husband, Labrodet. Instead of using signs, some of the parlor-house proprietors in Commercial and other streets affixed to their front doors or walls brass or copper plates, on each of which was stamped the street number of the resort and the first name of the woman who operated it. One brothel-keeper in Sacramento Street, who had formerly conducted a tea-room, achieved undying fame in the middle eighteen-nineties by nailing to her door a copper plate on which had been engraved this startling announcement: MADAME LUCY
YE OLDE WHORE SHOPPE.
Not unnaturally, this sign attracted a great deal of attention, but Madame Lucy removed it within a few days at the request of the police."
Here's a bit more on early San Francisco from the Herbert Asbury book and other sources. The opening video is from a 1905 film taken by an unknown photographer. It represents the only moving picture footage of San Francisco's main thoroughfare that has survived from before the Great Earth quake and Fire of 1906. It was only rediscovered by accident in the 1980's. This footage was taken only ten years after the Lumiere Brothers' early short silent films were first shown in Paris.
The large tower in the background is The Ferry Building, which mainly withstood the terrible 1906 disaster and still stands today. Many of the other buildings in this shot were destroyed. One Market Street Building to be burnt to the ground was the Palace Hotel, the largest and most opulent of its kind on the West Coast.