My DH and I are car-lite in Cleveland, OH. He has one to get to work, but I made him promise not to make me get a car ever.
I'd say Cleveland counts as a mid-size city - not big, not small. We're lucky to have some nice, extremely affordable, quiet urban neighborhoods. We love ours, and everything is pretty walkable. We're less than a mile from almost all the services we need (grocery store, chiropractor, library, post office, restaurants), and we have a corner store run by a lovely fellow named Fred that meets our immediate needs too. Public transportation in the city is more or less adequate, if you have plenty of patience and a sense of humor. I bike everywhere I can (well, not since I got so hugely pregnant... my balance is way too shaky for that right now), and I'm looking forward to getting a bike trailer to travel around with baby. I've been car-free for four years now, most of my family & friends think it's crazy, but they're used to it by now.
Most people in Cleveland own cars, so it's a challenge sometimes, but I'm accustomed to the lifestyle I live and I wouldn't get a car for anything
. So if you're looking for a small(ish) city, and if you don't mind fairly harsh winters, Cleveland's a great place to live car-free!