How can I only show one responsive menu on mobile devices?

Question

Here's my site: http://dev.shoeporn.com/

I'm running WP 3.5 and using this plugin: http://wordpress.org/support/plugin/responsive-select-menu

It is supposed to allow you to select which menus you want to be responsive, but it doesn't seem to work.

I only want the <div id="header-bar"> menu to be displayed to mobile devices, but currently <div id="header-nav"> is also shown.

I tried messing around with CSS but I think the "Responsive Select Menu" plugin javascript is overriding it when the page loads.

Any ideas?