Around where I live there are a lot of dry counties. I can always tell where the county lines are by the amount and types of broken liquor bottles. People road trip to the next state or county and get their supplies, then can't wait to drink a half pint of old crow on the way home. They toss it around the line. Its wild, a half mile or so of glass.
As to meth users, no they don't seem drunk, and I don't know about motor skills. But the general insanity and poor judgment of a tweaker should never be underestimated.