Being from BUF, there's no question who I'm always rooting for. Having lived in many NFL cities; DC, Chicago, Houston (Oilers time) and Seattle (AFC West), my best memories have been at a local BILLS bar with people who are mostly from WNY too. If you're from a city that does not have a team, I can understand "adopting" another team, but don't see that working for me, ever!
When we moved to the Richmond area, i expected to see a lot of Panthers fans but really, it's pretty evenly divided between Redskins & Cowboys fans so people have adopted their respective teams. I'd bet that most of the local Cowboys fans have never been to Dallas, or Texas!