Based on http://stackoverflow.com/a/11956132/1175496

google_geochart_pretty_labels.js

 function drawVisualization() {
    var data = google.visualization.arrayToDataTable([
      ['Country', 'Popularity', 'Display'],
      ['DE-BY', 200, 'Bavaria'],
      ['DE-NW', 500, 'Nordrhein-Westfalen']
    ]);

   //http://stackoverflow.com/a/11956132/1175496
      var formatter = new google.visualization.PatternFormat('{1}');  
      formatter.format(data, [0,2]);
   var view = new google.visualization.DataView(data);
      view.setColumns([0, 1]);  
   var viz = document.getElementById('visualization');
    var geochart = new google.visualization.GeoChart(viz );
   
   console.log(view.toDataTable().toJSON());
   geochart.draw(view, {width: 556, height: 347, region: 'DE', resolution: 'provinces', 
                        displayMode:'text', 
                        //legend:'none',
                        colorAxis:{ colors:['green','green']},
                        sizeAxis:{minSize:12,maxSize:12}});
  }