I lived in Manhattan for five years, so I should know this, but... What's the deal with strollers on the subway in New York? Assuming it's not rush hour, do you usually fold it and hold your LO and stroller, or keep it open?

I already know stairs will be an issue. Considering visiting a friend in Brooklyn while I am in the area and don't want to be a jerk- or inconvenience myself if it's not necessary.