Want a 1 sided texture with alpha.

I took for granted that my textures would automatically texture 1-sided, so I made a plane with alpha-mapped text, then duplicated and flipped it so it could be read correctly from front or behind.
Unfortunately, both set of mirror-imaged text render from both sides, and the result is a mess.

I really need my textured faces to be renderable from the direction of the normal only. I can’t figure out how. Please help? I’m using Blender 2.49b