Having been a barista and attended bar school; I would say you can cross-train
incredibly easy without going to bartending school.
It isn't a waste of money per se, I did learn more about the history behind
drinks, how to do a pour count, and some other things. But for me, the service
ethic I picked up as a barista has taken me farther along than the bartending
school.
But when you interview, stress customer service, what you know about making
drinks quickly, and the number of customers you served an hour at your coffee
house. It worked for me
--
"You two are alcoholics!"
"No. We're alcoholists!"
"And we'll continue to appreciate this bottle until it is empty!"