It's still quite a place to see, even with the degeneracy. Tell them to download that poop app, avoid street people, and be wary of sketchy individuals. I'd recommend a flight around the city and bay in a small plane. Maybe a boat trip to Alcatraz. All the usual tourist stuff can still be fun, you just have to remain situationally aware of the marginal people. I think you need California ID to enter a marijuana store, but that would be an amazing sight for some parts of the country.  They'll be fine if they pay attention to their surroundings and their gut.