I am not a city person at all. And I've only been to San Fran once and only for a week. But I fell in love (except for feeling like I was going to freeze to death in the summer). I walked every inch of the place up and down hills miles and miles for days and I'm pretty sure I ate at least 18 times a day. Only one place was 'posh', springy, and even at that, it was in a back alley with rickety wobbling tables on uneven bricks. My other favorites were a diner (the best California burgers), a pizza shop (with such yummy Italian sodas), high tea at The King George (so much fun).
And most favorite of all a tiny tiny tiny sushi place that seated at most 10-12 people if you really squeezed in, the husband cooked, the wife waited tables, we really couldn't understand her at all so I have no idea what half the stuff was that we ended up eating. We just pointed at anything that looked interesting. I loved it so much. It is one of my favorite dining experiences anywhere.
Sigh. I will be so jealous when you guys all go to San Fran and EAT there!