You could actually put the value = to the text and then do
$j(document).ready(function(){
$j("select#select_2").change(function(){
val = $j("#select_2 option:selected").html();
alert(val);
});
});
Or what I did on a similar case was
<select name="options[2]" id="select_2" onChange="JavascriptMethod()">
with you're options here
</select>
With this second option you should have a undefined. Give me feedback if it worked :)
Patrick