I can't give you specific advise about San Francisco, but recount my experience in Clearwater in July.
I visited Gordon's Jewellers during their sale (they are a nationwide chain). I bought a five stone diamond half hoop ring which was $1430 - discounted to $994. This exchanged to €836.
I have to say I was nervous in spending this amount of money - but I had had an accident while on holiday and wasn't able to spend money on anything else (fell and hurt my back). It came near time to go home and I dragged myself to a shopping mall for some therapy and ended up in the jewellers.
Lots of people admired the ring when I came home - so out of curiosity I had it valued.
First thing the jeweller said to me when I went back was "this is an American ring". My heart dropped. I asked how he knew and he said the settings are different to European. However, once that shock had passed he continued to tell me that the diamonds were of a good quality and he valued the ring at - wait for it €3,800. I nearly fell over!
This is my experience, it has been good - and if I find myself in the States again (with money to spend) I would definitely visit Gordons again.