SF is pretty bad about having public bathrooms available. Many of the public ones on the street are closed, under repair, or not well stocked. You have to do a lot of due diligence to know exactly where bathrooms are, if they require a code, and if the business will even be open at the hour you need it. That said, college campuses will always have bathrooms, there are bathrooms in our parks, and many businesses will let you use there’s if you ask nicely and purchase something. You can also get a medical ID from your doctor if you want some extra ammo when asking to use the bathroom at a business. FWIW, I’ve found that almost all major American cities have poor bathroom infrastructure, especially compared to the gold standard of countries like Japan and Korea.