Since we came to Portland, OR 12 years ago precisely for the reasons expressed by the o.p. I think I can speak to their concerns. Let's get one thing out of the way, however, even most Portlanders don't think car free is really possible here! A higher percentage of Portlanders are car lite than anywhere else in the U.S. but the actual percent of people that cycle here is tiny. Very tiny. I smiled when the opinion was expressed that Boulder, CO was not the best for a car free lifestyle only to have the example of a car free lifestylist that blogs about it yet be listed. That is exactly the case with PDX. If you really need (you don't) for a significant portion of the bike lanes to be protected you won't be happy with PDX's infrastructure.
I make a distinction between being car free by choice or car free by neccessity. I further distinguish between choosing a destination city known to be 'bike friendly' and being born in a city. There are cyclists living car free and using (or not) bicycles for transportation and/or recreation in every city in the country. If one is going to actually move a long way to be in a city known to have bike friendliness street cred, the short list really is down to the cities listed in the o.p. I would whittle it down even further: Portland, OR. Period. I'm not sure Davis, CA, Fort Collins or Boulder, CO or Madison, WI can be considered as reasonable substitutes for Washington, D.C. Portland, OR can. The metro core is 650K and the total metro area is 2.5M. Davis, CA is rural by comparison. If that's what you want, fine. But if you really want a city and not a rural town, then you want Portland, OR.
Cagers are going to be cagers the world over so don't expect cycling Nirvana. That won't happen until Texas is submerged and the oil fields all go offline. Until then, PDX is at least a place where bicycles are tolerated on most streets. Many are set up for considerable frustration for motor traffic to limit speed and crowding and delivering an enhanced cycling experience. Mass transit access is superior but the rail options will never equal DC or NYC.