Recommending to join the AMA won't help here. In order for the AMA insurance to cover an individual they must be following all the rules from the 2006 AMA Safety Code. One line in the safety code that usually excludes those individuals that want to fly wherever they feel like is this:
4. At all flying sites a line must be established, in front of which all flying takes place. Only personnel associated with flying the model aircraft are allowed at or in front of the line. In the case of airshows demonstrations straight line must be established. An area away from the line must be maintained for spectators. Intentional flying behind the line is prohibited.
Ken