There is allot of advertisement going on for Freedomain radio but ofcourse there is never enough. Many people share the links, post on other forums and social pages talk to friends about it. I'm not sure posting signs all over the towns would help much though it probably won't do any harm.
Stef always said and i agree with this that the best way of advertisement is living with integrity. Living your values will do far more then posting links or signs on walls.