I've been using a bike as my exclusive transportation in SF for about ten years. I've always ridden, but that's when I stopped driving a car except under extreme duress.
Here's how to begin your adventure as a commuter-bicyclist in San Francisco:
- Never take bike advice from anyone who owns bike shorts, clip shoes, a messenger bag, or a fixie. That's like taking car advice from someone who enjoys rebuilding carburetors.
(Update: If you are this person, you need not reply with your indignant "corrections". You are not the person to whom this advice is addressed.)
"City bikes" and "road bikes" are designed for some Jetsons-slick hypothetical future city that I've never seen. Or maybe for the bike paths in Los Altos or something. Here in real cities, roads are shit, and if you want your wheels and tires to survive curbs and potholes, you need a hybrid. They're a little heavier and a little slower. Are you racing? No? Then you don't care.
So, get the cheapest hybrid you can stand. Shocks are a waste of money. You should be able to get a pretty nice brand new hybrid for $370 or so. You can probably get a used one for a hundred bucks.
If you feel like you want a lighter bike so that it's easier to carry up stairs: don't bother. That's optimizing the wrong thing. You'll get used to it (by which I mean: become stronger).
Get a bike that's the right size for you, and has properly adjusted handlebars and seat. The shop will adjust it for you. If they won't, or if they tell you it doesn't matter, go to a different shop.
Get a u-lock. Lock through the frame and the back wheel. Your bike will be stolen, so don't get too attached to it. This also means, don't waste your money on junk like baskets and lights. Just get a backpack.
It doesn't matter how crappy your bike looks: any bike is worth stealing for $2 worth of crack. Your bike is temporary. Accept this and move on.
I always replace my front wheel and seat quick-releases with $2 worth of hardware store bolts, and then bend the ends over. This might have some negligible effect on theft. I refuse to be one of those people who lugs around 3 chains and disassembles their bike every time they park, so that's the trade-off I make.
The bike-nerd at the bike shop will try to give you smooth, high-pressure (110psi+) tires, because they are more efficient. But if you don't air them up weekly or more often, you'll get pinch-flats every time you hit a pothole, which is always. Also, the gas station air pumps often only go up to 60psi anyway. Get knobby low-pressure (60-80psi) tires and they'll last a lot longer. (If you do end up with stupid tires, you might want to get one of these.)
Likewise, make sure the tubes you get have the kind of connectors that the gas station air pumps take. Bike shop nerds like to fuck you with goofy connectors sometimes, out of sheer mean-spiritedness.
Bike maintenance: don't do it, ever. It's not worth your time. Just take it to the shop. Getting them to replace a flat for you costs $20 and takes 10 minutes, including the tube, and you don't get dirty.
It's a good idea to know how to change a flat, but why do it yourself when you can pay someone else almost-nothing to get greasy on your behalf?
Safety: I follow the Zodiac approach: always assume the cars can see you perfectly, and are trying to kill you. If an intersection seems iffy, use the sidewalk and crosswalks. If big streets like Market and Van Ness freak you out, there are always less traficky ways to go, or just stay on the sidewalks.
Do whatever you need to do to feel safe. You have nobody to impress.
Grocery shopping: yes, you really can do it with a single backpack. The trick is, shop small once a week instead of big once a month.
If you try to dangle bags on your handlebars, you will die.
Cross train and trolley tracks at a 45° angle or more, or you will die.
You really do need to tuck in or roll up your right leg. (You probably won't die, but you'll shred your pants.)
You don't need to ride up Haight. Take Fell or Fulton and then go through the Panhandle.
The City is only 7 miles across. Nothing is as far away as you think it is.
Update 2: Oh great, here comes the peanut gallery. Thanks, Cory Rob, srsly. I'd recommend against reading the comments here unless you're the type who reads comments on Youtube. Or maybe you just want to hear a bunch of fixie-hipsters with sand in their vaginas tell me how wrong I am and how you should spend a fortune and do all your repairs yourself.
Update 3: After getting 200ish comments on day one, I went through and deleted most of the redundant ones, and most of the ones from butt-hurt bike-nerds and mechanics. I've also turned on comment screening, and won't be approving new comments here unless you really have something new to say.
I'm a little (just a little!) surprised at the level of vitriol this one provoked. It's like I farted in bike-church. You'd think I was making fun of Linux or something.
