A lot depends on what the nature you're looking to be accessible to looks like of course. (And I'll be the first to agree that the Bay Area is probably especially nice in this regard.) But I'd say you were describing any significant coastal city, areas of Colorado (can't speak to other mountain states although places like Boise I would think...), etc. If you're looking for a reasonably affluent suburb there really isn't a particular shortage of them around the country--and many have good outdoor recreation options.