I am in the process of completing a personal move to San Francisco from the east coast. For me, where I live is primarily about the food. Specifically, the question I care most about the answer to is, "How many great restaurants can I WALK to from my home?".
I tried living in Manhattan (specifically for the restaurants) but couldn't handle the cold winter weather, so I'm back in my favorite city. (I lived in North Beach from '93 to '98). But the neighborhoods have all changed, South of Market is completely different, and I need help figuring out where to look for housing if my main criterion is restaurants in the area.
Again, what I care specifically about is how many great restaurants I can walk to. By great restaurants, I mean gourmet food - no denny's or McDonald's, but since I eat out 14 times a week, I over-the-top high end places don't work well. The problem I had living in North Beach was that every place there was too rich and/or heavy for every day dining (Zax was my favorite exception if anyone remembers it). I frequently eat alone, and therefore prefer restaurants that have a comfortable setting for eating dinner at the bar.
Several people recommended the South Beach (ball park) area, but when I checked it out I liked the modern living spaces available there but found the restaurant scene terribly limited. The Paragon (a frequent stop of mine in the 90s) has moved there, but only a few other places were open when I toured the neighborhood and the whole place seemed dead. I'm decidedly not a sports fan either, so the prospect of living next to the park wasn't appealing.
I ended up taking a temporary (3 months) furnished lease in Cow Hollow because I couldn't figure out where to live on my short househunting visit. Although both Union and Chestnut appear "lined with restaurants", on closer inspection it seems like there are only a few places (Betelnut, maybe Osha, Circa if its not thursday night) that I would frequent. But if there is a part of San Francisco that feels like Los Angeles, it's this neighborhood, and frankly I don't like that feeling (no offense to LA intended). I'm more of a down-to-earth kind of guy and prefer to avoid scenes where image and trendiness are considered important to people.
So where should I be looking in the city? I can afford a car but prefer not to drive one. That's why I like the city in the first place, besides the food. First priority is walking distance restaurant selection, 2nd priority is convenient access to public transportation. A lot of people have said So. of Market, but if there is a busy at night/happening part of SoMA, I haven't found it yet. It's sure not around the ballpark neighborhood.
The best advice you can give me is "For XXX, try walking down YYY street around dinner time". I have 3 months to go research neighborhoods before my short-term lease runs out, so I can do plenty of research.