As far as hunters shooting signs, real hunters have far better things to shoot at than signs. Those shooting up a road sign are the ones who should not have a weapon in their hands in the first place.
As for a .30-30 going through 1" steel plate, I would have to see that. 1" aluminum possibly. Should the material be steel it would take a full metal jacket to dent that material. Soft points will disintegrate on impact.
As for the signage, an inexpesnive vinyl sign silk screened at the local sign shop mounted on a painted marine ply backer board woudl last for a full season and be far cheaper than any metal signage you could purchase.
Bob C.