I've got about 400 or so models in my building each about 5000 polys each give or take. I am trying to increase the framerate a bit and was wondering if adding a code that made any entities not visible on the current screen not be rendered (once an entity got on the screen though it would render or vice versa) would work any to increase the framerate?

No, because that what you can't see won't be rendered of the engine. You may decrease the model polys, just taking some entities out of the level or decrease the textur sizes.