How does one learn to ride a bike in the busy streets of San Francisco?

The way I learned was riding on streets that aren't so busy. As you build up confidence you can graduate to more and more heavily trafficked streets.

Riding in traffic is not for beginners. You need to practice and gain competence in a safer environment. You can do this in places where there are fewer cars or where streets are blocked off. Look for parks or schools or large parking lots to practice in until you are confident in your ability to steer, start, stop and evade.

1) Ride in Golden Gate Park while the streets are closed until you get a feel for biking itself. I believe the  http://www.sfbike.org/?edu3 classes mentioned take place there, alternatively there are several bike rental places there.   2) Once you've gotten some confidence there I'd recommend trying biking along the bike paths along the Embarcadero - or biking across the Golden Gate Bridge.  Both of these have clearly defined bike lanes, some traffic, and good places to stop if you get freaked out. 3) Try biking in the Financial District on a weekend so you can figure out bike lanes and routes with less traffic. I'm not familiar with Nob Hill, but downtown and SOMA find good bike routes through the Google Maps bike layer, watch the bike lanes and watch out for 2 things:  Cars and tracks! Be aware that catching a tire in the tracks of the F line or cable cars will make you fall and has a chance of wrecking your wheel. Be aware of cars turning or going in or out of driveways especially, rarely will a car hit you by overtaking you going parallel - it's generally these 'from the side' situations.

It's not that different most other cities in terms of traffic and the ever present possibility of getting run over. If you've bikes in other large cities SF is not really any worse. I got around exclusively by bike in Washington DC for over ten years so I wasn't particularly intimidated by SF traffic. However if you are just learning how to ride a bike, as in the basic mechanics of staying upright, you probably want to spend lots of time in the park just getting used to riding and the 'personality' of your bike. You probably see those courier guys buzzing around with no hands through busy downtown intersections and think you can quickly get to that level of skill--but it takes awhile. First get comfortable enough with riding that you know longer think about it: get the point where riding becomes second nature. When riding in traffic you have to be attentive to dozens of details every second and prepared to act instantaneously--you have to anticipate what drivers might do (often based on watching them for only a few seconds to get a quick feel for their behavior), you check rear view mirrors on parked cars to take note of which are occupied and might 'door' you, you must constantly keep an eye on the road for debris and potholes, all the while timing traffic lights and watching out for pedestrians. Don't get yourself into that situation without becoming a competent rider first. Once you've gotten experienced on your bike and increasingly comfortable in traffic you can slowly do more urban riding. Maybe just stick to areas like the Sunset, the Presidio, Marina, and SOMA at first then work your way up to biking downtown and tackling hills around Telegraph, Potrero, etc, etc. SOMA is nice and flat with wide streets and very little traffic, and you could probably practice safely (just be careful with 101 traffic as it enters/exits the freeway)...but the speeds just aren't very forgiving around there. I would originally just stick to an area with a more suburban feel, where cars go max 20-25mph, and where there is a stop sign on every corner. You will get in accidents, and you will get scraped up--some accidents will be your fault and some won't be. Either way, the difference between a scrape with a bruised ego and quadriplegia/death is largely one of speed and power. Also please invest $25-100 to protect your most important possession: your brain. Wear a helmet. My head has bounced off both windshields and pavement in various accidents and I shudder to think how bad it could've been without one. SF traffic alone isn't really all that bad and moves slowly enough downtown that the real risks are doors and being cut-off by drivers who fail to do a head check (happens all the time, trust me). The taxis in SF are rather dangerous, but the real challenge is the hills. There have been a few where the grade felt quite dangerous riding my brake all the way down. In SF there's always an intersection at the bottom of the hill so you can't simply roll on through. I noticed on my jaunts up to SF (I went to school on the peninsula and lived on a suburban campus) that I would find myself peddling up some brutal hill completely alone, or going down some extremely steep hill, again completely alone. Then I would spend a little time along a flat road and see a fair number of cyclists. And then finally it occurred to me: the cyclists around there have flat routes they all know and use. Only an out-of-towner would push it up some of those hills simply to go from A to B. Friends have mentioned cyclist-friendly maps that illustrate the flatter, bike friendlier routes around the city.

Look for a local bike club.  They will probably have beginner rides to get you some training and used to riding on roads. Otherwise just jump in, ride cautiously And thereby gain confidence.

I ride 5 days a week to/from work from Ocean Beach to Potrero Hill.  Here's my biggest tips to you since you want to ride to work: 1) Always assume some crazy person or animal will jump out in front of you at any moment.  Pay attention ahead to cars parked on right.  Look for people inside cars who might open door on you. Keep hands on bars at all times. 2) Pay close attention to cars as you near an intersection.  See if they look like they  want to turn right.  Do not barrel through intersection even if you have  green light.  This is surest way to get killed by car turning right who  doesn't see you in mirror. 3) Don't be that stereotype who runs through stop signs.  Be courteous and wait your turn.  I find drivers often will wave me on when I stop, even if they were there first.  In this case, wave back thanks and just go, to keep traffic flowing. 4) Stay on streets with marked bike lanes.  This will reduce your fears about getting run over.  From Ocean Beach, JFK Drive in GG Park is the safest route for bikes in the morning, through the panhandle, then the Wiggle.  Use Google Maps.  They actually have a bike route mapper, to plan your best route for biking to work. 5) Buy yourself a 1 watt Planet Bike SuperFlash Turbo blinky light.  That thing is so bright, it's amazing even in bright daylight.  Turn it on at all times if you want maximum visibility.