For sketchers specifically: the Ferry Building on a Saturday morning (Embarcadero BART, Saturdays 8am–2pm) gives you the farmers market bustle plus the Bay Bridge sightline and the clock tower facade. Washington Square Park in North Beach has the church backdrop, bocce players, and enough foot traffic that sitting with a sketchbook doesn't feel odd. Dolores Park on a weekend afternoon in September — once Muni's J-Church or the 33 bus drops you at 20th — is dense with visual material and usually warm enough to sit for two hours.

If you want something with a schedule around it: Outside Lands typically runs in August, but the fall street fair season kicks in September with events in the Haight, the Mission, and SoMa. Check the SF Recreation and Parks calendar and the NPC events page for block-by-block closures that double as pedestrian-friendly drawing spots.

Practical note: if you're driving in from Reno, park once near Civic Center or the Castro and ride Muni the rest of the day. Moving a car between neighborhoods on a Saturday is how you lose two hours.

With two hours: Ferry Building at 9am, walk the Embarcadero north to the piers, sketch whatever stops you.