There are loads of walkable areas in and around Boston. Your posting to Cambridge and basically all of Cambridge is walkable and has access to public transit. The same is true of Boston and Somerville. Notice I say most. There are some little alcoves I don't think are great for car free life. But seriously you'd be hard pressed to find a spot in any of those three towns that are more than a mile from public transit and day to day resources.

I would check out "walk score" for any neighborhoods that come up as interesting to you.