While, I don't know THAT much about Lite-C and such yet, so I may be way off. But I think this is whats happening.
When you say exit sign, I am assuming you mean a sign, like, you would see a stop sign in the street, or a little sign that someone stuck on the side of the road, etc... In that case, I'm pretty sure you would use an actual 3d model for the sign, and then paste the texture of the sign onto it.
If you are talking about a sign on a wall or something, I don't know why you would go behind it, because if you go behind it, its a wall, so you wouldn't see it?