Using Chrome I can see half of your first menu that has a text like "Maquinaria".
I think that the menu is going to show inside its container.
Have you tried setting an higher z-index?
I have also checked with Developer tool and the overflow is correctly set to visible.
EDIT:
This is the code generated at runtime:
<li id="kwick_3" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; position: absolute; left: 225px; width: 200px; overflow-x: hidden; overflow-y: hidden; display: block; " class="active">
<a class="headlink" href="#">Productos<h3>Nuestros productos</h3></a>
<ul style="visibility: visible; display: block; ">
<li><a href="#">Maquinaria pesada</a></li>
<li><a href="#">Transporte</a></li>
<li><a href="#">Agroindustria</a></li>
</ul>
</li>
The UL element has an overflow (x and y) set to visible. but the parent LI element has its overflow (x and y) set to hidden