I'm not in a place where I can test but
try
Code:
if ( ($show['guest'] OR in_array($vbulletin->GPC['usergroupid'],'X,Y,Z') AND !$lvgbot AND $vbulletin->options['lgvon'])
Where X,Y,Z are groups you want to treat like guests (it can be just one group).
If that doesn't work then I'm calling the usergroupid variable incorrectly. In that case, try $vbulletin->userinfo['usergroupid'] instead.