I'm sure it varies by area, but in NYC I've never seen vegetables in a Walgreens (or DR, or Rite-Aid, &c.). They sometimes have milk and eggs, but it's usually the smaller packages (half a gallon or less / half a dozen respectively) and the dry goods that aren't cereal tend to be smaller or "instant" varieties (pouched rice and pasta is what I've seen). I think you'd struggle to healthfully feed an individual with just a Walgreens, much less a family.