We stayed at a hotel recommended by one of my co-workers.
It is called Hotel Milano and we highly recommend it!
This is the view from outside our window.
We were on the 4th floor and right across the street from the Mint.
We did have a smaller quiet queen room but it seemed too small and dark.
We changed rooms to a King and it still seemed really quiet and it was tons bigger.
The hotel is in the Union Square area and a nice walk to the ferry building or china town.
Accross the street is a residence hotel...not the best, but even at night it was not scary.
Very reasonable for SF.