The rotating green/white beacons are VERY visible in the New York area. I took off from Newark one evening in the back of a 737 and you could literally see dozens of them. By the way, they don't have to rotate, just flash alternate green/white.
But don't get confused between AD Beacons and ident beacons which are green (only) and flash the code letters of the airfield, usually the ones displayed in the signals square.
AD beacons can also be a flashing white light when approved by the CAA.
If you see red flashes when you expect green, you've found a military airfield.