We stayed in the Royal Pacific Motor Inn twice (three nights when we arrived to San Francisco and two nights before we flew back home).
It is centrally located at the border of China town, we could walk to many sights during the day (Fishermans Wharf, Cable Cars, Union Square, Market street) and for dinner in the evening.
We felt safe at night .
Try to get a room to the yard, there it is rather quiet although it is in the middle of town.
It was clean (except I didn‘t know what to think about the carpet in the rooms).
Checkin was easy and all personell is really friendly.