Depends if anyone sees you sitting in the car with your antenna pointing at them or not. If you have spent any amount of time reading posts here you would realise that this question might get people suspicious. Let me say that you are really better off not doing any sniffing of anything that doesn't belong to you, and we won't tolerate discussions of that here.
I will say that airodump-ng is designed as a passive sniffer, if that helps. If you want to confirm its not going to "leak" then you would need to test it, but if you're not doing anything wrong you probably don't need to worry about that.