SFO uses the PRM approaches only when the weather is in the 1200 / 2 vicinity and slightly above. This corresponds to the minimums for the LDA-PRM 28R approach. Significantly better ceiling and vis (that is to say 85 percent of the time) will get you vectors for the parallel visuals described in previous posts, whereas weather below that value will be below minimums for the LDA-PRM 28R approach and turn the operation into non-PRM (staggered) parallel CAT 3 ILS approaches.
Been flying in there very regularly (widebody) for a few years and hardly ever see the PRM procedure, can count the number of times on one hand. The dependent visuals where they precisely time your base leg vector to point you RIGHT at the guy you are following so you CAN'T POSSIBLY miss him, are the standard and a lot of fun.
SFO becomes much more sporty right before a cold frontal passage when the winds crank out of the southwest at 35+ knots off the hills, and you land into them on the 19's.
And regarding GA in the USA, I learned to fly in the Bay Area many moons ago, and used to take adventurous students into SFO to do night touch and goes around 2AM when the traffic load was light. In the world prior to high-speed Internet and LiveATC, they could only collect the landing fee if you stopped, you see.