In all of Pinellas county, FL (pop. ~1 million) there are only 2 rubber surface tracks in the whole county. One at a private school and one at a public school. I have sought permission at both as well as many of the other asphalt tracks. Every single facility is locked up and has no trespassing signs posted.
The irony of it all is that there is a really strong running community here. It just doesn't make sense. I think it's the responsibility of the HS track coaches to be a liaison to the running community. Most of the dedicated runners in the community can serve as role models for continuing to run beyond school athletics.