Visiting us in SF? If you have a car, here are some day and 2-day trips not far afield.
Wine country: Napa is closest (~1 hr), but Sonoma/Mendocino are more chill (1.5-2 hours). It’s getting hard to find mom-and-pop wineries there—everything is very commercialized and most places charge for tastings. That said, Mumm has interesting champagne cellars you can tour and a lovely outdoor tasting deck. Avoid weekends at all costs; it’s mobbed. We have maps of the region showing various wineries.
Santa Cruz Mountain wineries: The Santa Cruz/Monterey growing region produces lovely chardonnays and pinots (vs. the zins, merlots and cabs for which Napa/Sonoma/Mendocino are more known). And there are many more mom-and-pop operations that are more intimate and casual. Allow about 1.5 hours drive along the fast route (I-280 to CA-17 or CA-84) or 2 hours along the scenic route (CA-1 or CA-35 along the ridge). We have maps of the region showing various wineries.
Santa Cruz: Hippie/surfer town, amusement pier, and great fish restaurants. Can be a lunch stop on the way to Monterey if you drive that route. Right next door to achingly cute Capitola.
Monterey/Carmel: Its Cannery Row/Fishermans Wharf are no doubt touristy, but still lovely for oceanside dining when weather permits. The Aquarium is world class and includes indoor and outdoor exhibits emphasizing local fauna but with a good selection of exotics too. Expensive to stay here. 2 hour drive by the fast route, 2.5 to 3 by the scenic (coastal) route. Carmel is another ~30 minutes beyond that, and equally cute, though there is less to do; but plenty of good dinner options.
Big Sur: A challenge to get to right now due to the bridge and road washout; extremely remote by any standard. San Simeon/Hearst Castle is nearby but I personally find it less compelling than the crazy scenery. Allow at least 2.5 hours driving each way, plus sightseeing time.
Sausalito: No car required! Take the ferry there from the Ferry Building or Pier 39 (ask us for maps/timetables), or if adventurous, rent bicycles next to the Ferry Building, bike across the Golden Gate Bridge, and take the ferry back with your bike. A nice lunch/brunch stop, and if you have time, visit the fascinating SF Bay Model, constructed by the Army Corps of Engineers to evaluate whether landfilling the entire Bay would be a good idea (no). ~20 minute ferry ride from downtown SF.
Golden Gate Bridge: The car parking plazas can be a pain, but the true experience of the bridge is obtained by walking or biking across it, which means you either park at one end or bike there (or you can Uber, or take the Golden Gate Transit bus; ask us for directions).
Yosemite: A bit ambitious for a day trip; 4.5 hours each way to the valley. Ask us for recommendations of where to stay outside the park (it can be tricky to get campground space inside the park in high season; there’s a couple of lodges including the beautiful and expensive California-Arts-and-Crafts Ahwahnee, on which Disney’s Grand Californian hotel is based, but they also fill up fast.)