As mrbb said .. There is allot of public land that is land locked and not accessible without written permission. If that's the case you need to talk to the land owner and see if they will allow you to access the public area.
I personally think that public lands should have some type of access right of way. But that would be very difficult in many places, and it just isn't how it works.
If it is in fact public land that somebody is wrongly trying to keep people off of- Report the signs and then go hunt it
-Jake