O'Hair Park is for the Dogs

I and a few friends walk from Sutro Avenue entrance of O'Hair Park to Stafford Lake on a regular basis. The sign at the entrance states that dogs are to be leashed. This is rarely if ever observed as the dog owners use this passage to get to the dog park, which is about a half mile away. Usually there are at least 3-4 dogs running while their owners walk.

I understand that a dog running free is beneficial for the dog, but not for us walkers. Many times the owners throw a ball from the bridge over the creek and into the water allowing the dog to retrieve it. On several occasions the dogs have come running up to us and go for your hand or even worse other body parts.

Who enforces the leash law that is in place? Why aren't the dog owners picking up their animal's feces?

Is O'Hair Park just for the dogs and an extension of the dog park?