My suggestion: Racetrack 05
This track have 4 x 3 signs in the north part of the track and 1 x 5 in the southern part. Makes 17 signs total per lap. I only obtained 3% the first runs until i realized something.
Your car needs to connect to the object you destroy. If you simply drive through the signs it's sometimes not the car itself that destroy the object, but the object you destroyed before and is in front of your car. So for the full progress you can't simply drive through the objects.