Create a specific model for the web content.
In this model, the user can be obtained by velocity.
http://content.liferay.com/4.3/misc/theme-api-4.3.0.html
It's something that comes to mind for your problem.
Another thing, it would get this in the user's session by javascritp. But I think it is not possible then. The session belongs to the server and javascript is executed on the client.
Otherwise, modifying the content web portler obtaining the values contained in the session by JPS (for example). and make them accessible for display in the portlet.
