Like oldnslow2, speed limits for the MUPs around here are 15 mph for everyone. Faster just isn't safe for the pedestrians on it. Enforcement? I'm sure if there were enough complaints the police would patrol it more for a while.
If you want to go over 15 mph, you should probably be on the roads anyway. You may feel intimidated by cars, but that's what you're doing to the pedestrians right now.