You could try something like this:
In admin-menu set mod_login show up in module-position "user2".
In index.php of your template, insert the following code at the position where your login-module, or your logout-link should appear.
Code:
<?php
if ($my->id) {
mosLoadModules ( 'user2' );
} else { ?>
<a href="<?php echo sefRelToAbs("index.php?option=logout"); ?>"><?php echo _BUTTON_LOGOUT; ?></a>
<?php } ?> Now position "user2" is only loaded when an unregistered user is viewing your site.