I'm going to park in one of my neighbor's unassigned parking spots.
Why are you going to do that?
I'm sure they'll come out and request for me not to park there, so why not just park there and get away before they do so?
Even though the parking spot is unassigned it does still belong to your neighbor. It wouldn't be right to park there without getting permission first as you don't know for sure if your neighbor might need that parking spot or not.
Nah, fuck them.
You do not have the right to park in your neighbor's spot as you have no okay from them to do so. Don't try to sneak around and get into their spot, just don't park there or you risk a real rift with your neighbors.