If your going to use vinegar, go light. It is also used as a herbicide....
http://gardening.about.com/od/naturalorganiccontrol/qt/Vineger_Herbici.htm
Just ordered some Horticultural Vinegar for just that purpose. Couldn't find it locally. Need to kill some seedlings in the rocks out front. HeHe Maybe it'll adjust the PH while it's at it?