function yourmodule_form_alter(&$form,$form_state,$form_id){
   if ($form_id == "your_views_exposeform") {
            // first try dpm($fom); to see what you have there
            foreach($form['expose_your_field']['und']['#options'] as &$item){
            //  repalce label of select option items with what you want
            }
        }
        }