Whenever someone talks about how dirty SF is, you know they confined themselves to SOMA, TL, the Mission and maybe North Beach. The rest of the city is about as clean as any big city in the US. There's nothing particularly dirty about the Sunset, Richmond, Pac Heights, Cole Valley, Parnassus, Diamond Heights, West Portal, Forrest Hill, Russian Hill, Glen Park, or the other neighborhoods that make up most of San Francisco.
In contrast, I now live in NYC and while there are no distinct "human poo" neighborhoods as there are in SF, the entire city is covered with a layer of grime and garbage from Manhattan all the way out to the furthest stops in Brooklyn and Queens. This was simply not the case where I lived in SF, on top of 17th street.
The same applies to the weather. Anyone who thinks SF has great weather has never spent much time west of Twin Peaks. It is foggy and cold most of the time.