[amykhar]

You may not need to query the forums at all. It might be available in the cache. I used a simple bit of code:

$forumchoice = array();

foreach (array_keys($vbulletin->forumcache) AS $forumid)
{
		$forumid = intval($forumid);
		$forumperms =& $vbulletin->userinfo['forumpermissions']["$forumid"];

		if (isset($vbulletin->forumcache["$forumid"]) AND ($forumperms & $vbulletin->bf_ugp_forumpermissions['canview']) AND ($forumperms & $vbulletin->bf_ugp_forumpermissions['canviewothers']) AND verify_forum_password($forumid, $vbulletin->forumcache["$forumid"]['password'], false))
		{
			$forumchoice[] = $forumid;
		}
}

to get me all of the forums that a user was allowed to view. You could probably use very similar code to get the ones that they can post in.