I have had numerous experiences with roadways where the speed limit is not accurately marked, or is confusing, where it switches back and forth or where it is not marked at all, and you have to know the default speed. I assumed that the car would be able to detect signs, traffic lights, etc. But that is not always enough to escape the attention of speed traps.
This will be trivial to prove in court because the robot car will be storing video from all cameras, as well as its debug log, in some sort of a "black box." As you, the owner, are not required to pay attention to driving, it will be one machine (the car) vs. another (the government.) If the car could not see the signs, it will be clearly a fault of the government because the robot is an objective judge of what is visible and what isn't, down to the last pixel.
I would rather prefer this scenario because it would be unfair when an LEO accuses the driver of not following the rules when those rules are poorly presented or missing entirely. As a human, you cannot present evidence of what you saw. As a robot, the car can do that. After a short while the police will switch from hunting the drivers to "programming" the cars by maintaining the signage. A passenger in a robot car, just like in a human-operated bus, won't be responsible for following the rules of the road. This will remove a considerable percentage of abuse of power by LEO, as they won't have as much power anymore over the occupants of the vehicle.