I have been to San Francisco in Novemeber twice and in February twice and had both extremes! Once in November it was sunny and warm (60's) and once it was cool (50's) and overcast. I have had the same experience with my February trips. The San Fran climate is more changeable than you perhaps expect for California because of it's geographical nuances, so you never really know what to expect. I think it is fair to say that it is typically warmer than the UK and can have what we would call "nice" weather but it is not a given.