Most of the larger, older cities will have neighborhoods that are walkable, though the city as a whole might fail to meet expectations. New York, Boston, Washington DC and Baltimore come to mind. But, they tend to be very expensive places to live (at least in the nicer areas).
Small and medium sized college towns (<100,000 residents, maybe) usually fit the bill as well. But, have the downside of many seasonal tenants and the other things you'd expect with a heavily young-adult-oriented area. But, even in these, you sometimes find you need to drive to a strip mall for big grocery runs - America doesn't really do small neighborhood markets and the price of real estate often drives grocery stores to the outskirts of town.
Small and medium sized college towns (<100,000 residents, maybe) usually fit the bill as well. But, have the downside of many seasonal tenants and the other things you'd expect with a heavily young-adult-oriented area. But, even in these, you sometimes find you need to drive to a strip mall for big grocery runs - America doesn't really do small neighborhood markets and the price of real estate often drives grocery stores to the outskirts of town.