Well, it depends how the join element was hidden. If you select "Hidden" under the main Options, then no. What that does is adds the element as a simple hidden input on the form, like <input type=hidden value="123" />. The element is not "rendered".
If you want to have an element which can be shown and hidden through JS, you have to leave "Hidden" unchecked, and add a "load" event on the element which you want to control the visibility with, which shows or hides the join element as appropriate on load. This is in addition to the 'click' or 'change' JS events which hide/show your join.
-- hugh