that card is more than sufficient for low settings.
on low settings(AA and AF off), i get 50% GPU usage on my HD5470M mobile gpu.
so a 6670 will definitely be smooth for low settings.
i am more concerned about your cpu. skyrim is quite cpu dependent. i would suggest to OC your cpu as much as possible for a good gameplay.
3.33ghz and higher should be OK.
i dont think you can get more than 30 -ish FPS from that cpu at this speed, despite any GPU.
and disable all shadows in settings. shadows are done by CPU in this game.