I had a similar situation to this a couple years ago except in my case the speed limit was not posted between where I got on the road and were I was stopped. I went to court over it all I got was a smart ass remark from some worthless judge and a wasted day.

Now I drive the speed limit not 5 or 10 over and if it isn't posted I go 30 on streets and 55 on highways until I see a sign. This results in being tailgated by some jerk most of the time.