Here's a tip for those flying into the international terminal at SFO. The wait for taxis at the international terminal is almost ALWAYS longer than at the main terminal. So ride the train to the main terminal and catch a cab there.
Unfortunately SFO uses cab bosses to load the cabs which means EVERYTHING is slower than it needs to be. If you can arrange private transit out of the airport you'll always save time.
The best way to avoid cab lines at SFO is to just hop on Bart. It's a 25 minute ride to downtown and you'll pop out of the ground right across the street from the Marriott. It costs all of $5 and never gets caught in traffic.