As I understood it, the A11 & A17 sites are the ones NASA really wants to protect. A11 for its obvious historical significance, and A17 because it contains numerous long-term environmental exposure tests that should be examined in a carefully controlled way when the opportunity comes. The other sites are open, but you should still not touch individual artifacts.
I think that if a robotic lunar mission starts to become real, you'll see some serious discussions between them and NASA over which Apollo site to visit and exactly how to visit it. NASA won't want to give up the opportunity to see what has happened to those sites either.