USA Holiday

Whereabouts is it, faringdon59? We were in San Francisco for a few days on a California trip and our hotel was on the edge of the Tenderloin district (apparently named because the local police get so much overtime in there they can afford the best steak!). We were told we'd be fine as long as we turned right and not left when we went out, and so it proved. We never felt unsafe there, though it is a very lively and diverse city. I'd love to go back, and I'm sure you'll have a great time.

If you are in Tenderloin, always walk toward Union Square or Market street. They are only a couple of blocks away bordering the area and are where the major shops (Sacs, Bloomingdales etc) are. There are lots of beggars on the streets, but they don’t usually hassle people.
Of course if you are in a poor area it is not wise to get out your phone or camera.

I'm sure the hotel staff will advise you about where is safe and where isn't, Faringdon.

We visited San Francisco in 1983 when DS was 6, DD1 was 2 and DD2 was 6 months. I would just love to go back.

DS lives in America and DDiL is American. They were horrified to hear that MrA and I had got lost in Baltimore last year and strayed into an area that we really shouldn't have. But we lived to tell the tale and I think generally in the 'bad' areas, the locals are more interested doing horrible things to each other, rather than to tourists.
I hope you have a great time

I've not been to SF but have have been to Ca many times (as well as the rest of north America. Its pretty much the same as everywhere else in the world in the respect of good and bad areas. As the post above says generally keep out of known bad areas and if you find your way into one by mistake then make your way out ASAP.

Hotel staff will normally guide you on where not to go.

If the area looks really bad and the hotel is as bad then don't stay there, Hotels are numerous and usually can acomodate without reservations.

Enjoy the trip.