FS SF is fine but not as good as the St. Regis nearby and it sounds like you are on vacation so not where I would choose to stay (service is spotty, even the concierge is pitiful most of the time). FS Palo Alto is an adventure (less so than when it first opened), but it is basically a real estate play that fizzled with the end of the silicon valley boom ... you'd be much better off staying at the RC Half Moon Bay for example.

As for Post Ranch Inn, it really depends upon expectations and price point (the good rooms are USD 1000-2000 with a big step down to the cheaper rooms). It is "rustic luxury" with a stunning setting but mediocre construction to dated standards; so don't expect an Aman in any respect. Personally I prefer Ventana which is more rustic, private and secluded with better views (when the fog is out) and cheaper .... but suffers from similar "rustic luxury" being not so luxurious for some.

I haven't heard of Cass House before but looking at the web site, it is charming B&B which is good value (1/3 the price) but a completely different experience. Either buy up to the high end in Post Ranch or consider Ventana instead.