In Illinois, predominantly the cable company runs the public and educational component, and the government component falls to the municipality. There's no way to determine audience like there is in broadcast. Electronically they have not come up with a device for measuring it. You must rely on surveys that are done in your community. The whole idea of doing this type of programming is not to gauge how many but to disseminate the information and put it out for consumption.
Public service is an arbitrary thing.
People will pick it up and comprehend it at their own level. It doesn't involve making money. You're not allowed to advertise, sell products or any money-making project. It's for education. Many park districts that use it educate the public about all their programs.