Is Outer Mission in San Francisco walkable? Well that depends on what you mean by "walkable".
On the one hand, you can get to everything you want to by walking. It is a relatively flat neighborhood with sidewalks and there are grocery stores and restaurants you can walk to.
On the other hand, this just doesn't feel like a walk around neighborhood in the way that North Beach feels like the kind of neighborhood you walk around in. Maybe it is because it borders a big freeway. Or maybe it is because it just feels a touch unsafe, I don't know.
So, I guess my answer is "so-so."