Of course a self driving car should be able to speed. My understanding is that speed limits are set by measuring the speed people are driving on the road and then determining a speed at which roughly 15% of the drivers are exceeding that limit. There is an expectation that people will speed, but by setting the speed limit a little bit lower almost all traffic will fall under safe bounds. Driving 38 in a 35 zone is completely reasonable. I probably would have been going 45 - 50 if the road was empty. If self driving cars aren't allowed to speed, they're going to be a nightmare for passengers and other drivers. Obviously different people have different feelings about the issue of speeding, but personally I lose my mind when I get an Uber driver that's driving to slow. Try and think about what it would be like if a computer followed every traffic restriction to the letter of the law rather than driving like an actual human.
People will vote me down because the idea of a speeding self driving car sounds scary, but I personally can't wait until the software has advanced to the state that it can confidently drive 200 mph on the 5 from LA to the Bay Area. (Presumably they'd have to build a much bigger better 5, with special lanes dedicated to autonomous vehicles)