Smaccoms, I lived in SF for 15 years without a car. It has one of the best public transit networks in North America and there are other fun options, too. I was one of the first 100 people to join CarShare and now there are thousands of members. (Local lingo tip: in San Francisco to make a quick U-turn is to "flip a bitch".)
The Mission is reasonably safe and has some awesome shops and restaurants. I used to live right on Dolores Park, halfway between the Castro and the Mission. As that area is the transition from one to the other, some called it the Transmission. (People in the City are fond of making up new neighborhood names.) When I first moved in, the area had a lot of prostitutes and drug dealers; now it's the gourmet ghetto and lures people from all over the City and even further. Plenty of wonderful markets, bakeries and restaurants. Be sure to put
Bi-Rite Market, Bi-Rite Creamery and Tartine bakery on your list... you can look them up online and whet your appetite. And I've never found a supermarket like
Rainbow Grocery anywhere else (a homo-friendly worker cooperative - they're closed on César Chávez's birthday and Gay Pride Sunday). They have
everything cool you can imagine.
Every day can bring unexpected sights. Tim Redmond, editor of the SF Bay Guardian newspaper, moved to the City from Oregon and in the first few weeks was unsure whether he'd stay. Portland is kind of funky, too. But one day he was walking down California Street from waaay up on Nob Hill, and he looked over his shoulder to see a guy skateboarding down the long, steep street, past a cable car full of tourists, wearing nothing but a jockstrap and a cape. At that moment, Tim knew he'd found his new home.
I stayed in SF long enough to watch it become a very different city from when I moved there. In my early months and years there I became friends with Herb Caen, shopped at Whole Earth Access, ate at Ti Couz and rode the 26 Valencia. All are gone. In their place are new faces and new places. What's still there, and a hallmark of San Francisco, is the energy of activism. I've never lived anywhere where so many people were so passionately involved in so many causes. (Actually, western Mass can be a little like that.) After living through a couple of transformations of the City I figured it was time to try a completely different corner of the country. If you do make it out to Bagdad by the Bay, jump in with both feet. Explore relentlessly and select the best parts that complement or challenge you. You might not ever want to leave.
Call it "The City" and people will think you've lived there awhile, or are at least informed 
