Try this :
$('select[name^="salesrep"] option[value="Bruce Jones"]').attr("selected","selected");
Just replace option[value="Bruce Jones"] by option[value=result[0]]
And before selecting a new option, you might want to “unselect” the previous :
$('select[name^="salesrep"] option:selected').attr("selected",null);
You may want to read this too : jQuery get specific option tag text
Edit: Using jQuery Mobile, this link may provide a good solution : jquery mobile – set select/option values