I have something like this:
<rich:menuItem value="Go To" disabled="false"> <a4j:support event="onclick" ...> <a4j:actionparam .../> </a4j:support> </rich:menuItem>
<s:button view="/mySite.xhtml" value="MySite">
just define submitMode="none" and place h:outputLink inside. or use onclick with the same none mode.