I think just seeing the green slim stains on their t shirts put me off from having some coca leaves. Did you travel on the Yungas Road from La Paz down to Coroico on the mighty death road? My friend said to me some of the bus drivers drink alcohol driving those buses down the Yungas Road. So instead we decided to trek down the route on mountain bikes instead. I would sooner have more control of my life travelling down that Yungas Road than some bus driver under the influence of alcohol.