Not everywhere. Salt Lake City for example has wide streets and multi-story underground garages to allow locals and commuters alike to drive to the city, with a walkable city center above the garages. The newest residential buildings in the city also advertise their double-walled soundproofing between units.

One issue I have with a lot of smaller cities with walkable cores is that you run out of choices pretty quickly. I'm familiar with a number of places in that vein and they're fine to visit once in a while but I think I'd tire of them as an example of "city living" pretty quickly if I were looking for that sort of thing.

- SF is going to be a lot more crowded, noisy, less clean, obvious signs of poverty. Nothing you can really do to address it other than be aware that some areas are best generally avoided.

- On the other hand, SF has a lot more culture, restaurant variety, and is just a more interesting urban environment than SLC. So, basically, take advantage of that. SF, more than even most larger cities, has a huge number of interesting nooks and crannies to explore.

- Generally speaking, smaller cities often do have some degree of walkability in a central core but you're still crowded in to some degree while you lack the variety and opportunities that preferred large cities have to offer. (I'm not personally much of a fan of smaller cities. I think they tend to have city disadvantages without giving me offsetting benefits.)