As a native New Yorker, who has lived and ridden in all Five boroughs I have to say that it's not so much where you are as who's there with you. NYC is nowhere near as dangerous as it was when I was growing up. You need to keep your wits about you, and keep moving, but you are in much more danger from the traffic situation, bad streets, and the current general hostility towards bikers, than you are of getting attacked for your stuff: as long as you don't look like Bambi. You do need to know where you are though. It pays to study up on the various neighborhoods for your own safety. If you are new to riding in an urban environment, be conservative in your riding strategy. Also realize that it takes time to get to know the streets where you will be riding, in a physical sense: by that I mean actually knowing where the potholes, traffic nightmares, etc., are. You can't just blithely blaze along, your first time out, without risk of injury. Riding a bike, here in particular, always involves risk. You need to minimize it as much as possible by thinking your individual situation through: thoroughly.