Why not making some “From” and “Till” values (as default) for the selects and setting the fields as required?
If you need jQuery, you should use the simple selects, not the data selects. Otherwise, you can try something like this:
(function($) {
$('select.field-class').find('option').first().text('From');
$('select.field-class').find('option').first().text('Till');
})(jQuery)
Useful link:
Adding custom javascript to fields
