Actually, the way I do this takes a little monkeying around, so don't feel too bad.

First, under the Shading > Shading Options menu, I turn on "Wire on Shaded." (The shading menu is in your view port and not at the top of the screen with the rest of the menus.

Then, apply a material to your object, like a new lambert, and make the transparancy of the material all the way down. Now, the geometry is invisible, but the wire is still visible.

I generally make a Set Driven Key control to make it easier going back and forth to the material attributes.

Good luck!