Locutus wrote:
I plan on builing a router fence that sits on top of my table saw fence,
would laminated MDF be a good choice of material for the face?



It's worked great for me. Be sure to laminate both sides of the work
surface to keep it flat if you're not attaching it to some sort of
reinforcement. Most Biesemeyer-style table saw fences are either MDF or
birch ply under the face laminate.

In some cases, like spot made special fences, I don't even bother to
laminate the face. I simply paste wax the MDF and use the fence.