These cars are not preprogrammed; they look at signs and road markings. This is necessary to drive in construction zones and on new roads. As result, these cars always obey the law. As an owner, you will only select the destination - and, if desired, the route. (The car may know which route is shorter, but it may not know or care that the green arrow in one specific place is on only for ten seconds every five minutes. But you do care about that.)
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.