LA vs San Diego vs San Fran

Hi all, I'm a 26 year old single guy from London in the UK and was recently offered the opportunity to move with my company to one of LA / San Diego or San Fran for 2 years. I would have a friend(ish)in each of LA and San Fran and my direct boss would be based in San Diego, but beyond that I would not know anyone.

I know San Fran is technically not Socal, but it would be great if anyone could give me an idea of the different characteristics of the cities and which might be easier to make friends and generally settle in. I do like sports in general and going to bars / restaurants etc. and the idea of living somewhere warm really does appeal. Really appreciate any help at all!