That's not what toggle is for... check the jQuery documentation: http://api.jquery.com/toggle/
Just use the click event and keep track of the status yourself one way or another. Here is a working example based on your fiddle:
$('#open_menu').click(function(){
if ($(this).hasClass('toggled_on')) {
$(this).removeClass('toggled_on');
$('#content').animate({ left: 0 }, 'slow', function() {
$('#open_menu').html('Menu');
});
} else {
$(this).addClass('toggled_on');
$('#content').animate({ left: 250 }, 'slow', function() {
$('#open_menu').html('Close');
});
}
});
This uses a class which is suboptimal, so unless you need it for something else just use a variable instead.