I've been many times in the USA and especifically un SF. I have always found it a very nice and friendly place where I can just be myself and act like I do elsewhere, is not that different from Europe in my opinion.
I've been in SF in exactly those months and it was rather cold. Long pants and a notmal jacket should do the job, but since you come from the very north you can probably go around without t-shirt
One of the trips was from LA to Canada and the way back, around 10.000km in a Cadillac Escalade and was awesome. Not a single problem on the road, never drove in a dangerous area by mistake, not a single ticket and very easy to drive and park.
I think people who hate the USA is because they only want to see the political side, which I must agree, sucks big time, but it actually is a wonderful country full of nice people, at least that's my impression after my many visits.