How do I test for node type to print a variable from template.php?
Each template has a different set of variables available. The variables available in a given theme is generally documented in the comment section at the top of the file. You can consult this documentation on http://api.drupal.org.

The node type is not directly available as a variable in the page.tpl.php. However, you have the $node object which has a type property:

function MYTHEME_preprocess_page(&amp;$variables) {
  if (!empty($variables['node']) &amp;&amp; $variables['node']-&gt;type == 'NODETYPE') {
    $variables['greeting'] = 'Custom Greeting';
  }
}