The info window should open up automatically for you when you see the map load, the line of code that does this is in the wagmp_map_1.php file and looks like this:
marker_0_<?php echo $Recordset1_id; ?>.openInfoWindowHtml(address_0_<?php echo $Recordset1_id; ?>.infowindowtext);
It would have your recordsets name in it. If you can post back with this file I can check it to see if this line of code is in there and check why it might not be loading for you. Also, are you just displaying the current default location when the map loads or are you also displaying driving directions when it loads?