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?

Sure. My only recommendation would be to either leave the MDF
unfinished, or finish all sides the same way. I had an MDF/hardboard
laminated router table fence warp on me, and the only thing I can
figure out is that uneven finishing between the 2 sides led to warping.
Baltic birch ply is also a good choice, or HDPE/UHMW plastic would be
ideal if you don't need a lot of stiffness.
Good luck,
Andy