I said I would try it and post back...
For the test I used a pint of white vinegar + a teaspoon of salt, in a small spray bottle. It sort of worked on the lighter weeds after two days, killing the leaves, but not the stem. It had no noticeabel effect at all on the woodier weeds. It has been constant heat and sun for the past week since applying, until a light rain shower this morning - if that might have made any difference.