I agree. If self defense is what you're after, Kendo won't be an especially time efficient activity. You will gain a few things that would be useful. An ability to carry yourself well, a certain understanding of some principles that might help, but your time would be far better spent in a good judo, or karate program if your goal is to be able to save your skin a bar brawl.
Breaking down bad habits,
and building new ones.