I wear it on my sleeve. I lived in NYC and now NJ. A lot of people is these two states are "transplants". If you were to go to the city and walk around, you'd see just as many people wearing other team's apparel as you would see Jet's and Giants apparel. That is why it is tough to win in NY. People (usually Jets and Giants fans) think many of the locals are "turncoats", but they are "transplants" rooting for the team that represents the state they are from. If someone moves to NYC from San Francisco, they will still root for the 49ers.
I root locally for baseball and hockey, but when I see an Altanta Braves hat on someone's head or a Detroit Red Wings jersey, I don't think anything of it.