Display check marked taxonomies as drop down menu

If I understand correctly, you want to display the taxonomies you selected in the admin UI when you display your custom post type in the frontend. What you will need to do in that case is to modify the template file that displays your post, and use something like (adapted from content-single.php under TwentyEleven:

<?php $scent_list = get_the_term_list( $post->ID, 'scents', '', ', ', '' ); 
      if ($scent_list): ?>
          <span class="scent-links">
              <?php printf( __( '<span class="%1$s">Scents</span> %2$s', 'twentyeleven' ), 'entry-utility-prep entry-utility-prep-tag-links', $scent_list);
                    $show_sep = true; ?>
          </span>

<?php endif; // $artist_list ?>

This will display a list of the scents that are selected, but you could modify that output to show it as a dropdown list.