Time for CCTV & a VCR?
I think it would be great to wire the signs so that when they are touched, it gives a hugh electrical shock and sets off an alarm, turns on a motion light and takes a photo all at the same time. That should deter some of the theft. If you are worried about liability, put a warning sign, but since they are stolen at night the thief would never see the sign but your butt will be covered in court. After the word spreads that signs are wired, put the warning signs near all Bush signs whether they are wired or not. Maybe I could patent the idea, electric fences for political signs.