How to change default value of taxonomy term in View exposed filter drupal 7?
To display Results Only when Criteria is selected :


In your view, change Advanced Settings -&gt; Exposed form style to Input required 





In Exposed Form style settings you could define the text to be displayed on no results




OR

To Alter Exposed form options:


You need to implement hook_form_alter()
Here is a sample code of it:



function mymodule_form_alter(&amp;$form, &amp;$form_state, $form_id) { 
    case 'views_exposed_form_id':
    $name = 'Vocabulary_name';    
    $myvoc = taxonomy_vocabulary_machine_name_load($name); 
  $tree = taxonomy_get_tree($myvoc-&gt;vid);     
    foreach ($tree as $term) {        
     $tax[$term-&gt;tid] = $term-&gt;name;  
    }     
    $form['field_taxonomy']['#options'] = $tax;  
}