No one can answer that question definitively, Cricket.
Since it is not legal to park on the sidewalk, there's always a risk involved. It may be possible to get a ticket even without your plate, and you could be towed.
But that might never happen to you either. It usually depends on the whims of the traffic cops in that area, and whether or not complaints are made about where you've parked.
There are also crackdowns occasionally.
But as we all know, parking legally in the street is not without it's own set of risks (damage, theft).
So, do what you're comfortable doing, with full knowledge of the risks involved!

P.S. Neil recently wrote an Op/Ed piece for the Times on scooter parking in NYC that's
definitely worth a read.