Craigslisting for karate?

If I post an ad on Craigslist for a once-a-week karate partner here in Eugene, how will I know whether the person who responds is actually sane? What with all of the people I see talking to themselves on street corners in this city, the odds seem slim at best. Yesterday as I sat wolfing down my ever-so-nutritious chicken strip lunch, I noticed that two out of five people walking into Fred Meyer by themselves were speaking to some invisible entity; I kid you not--I tallied. I think it's the fumes from the mill north of Eugene that drive its citizens to senseless self-talk.
But I guess self-talk is fine. Whatever. When I worked in data entry, recording cherry genetics statistics alone in a room for eight hours on end, I certainly talked to myself: and in a fake British accent, no less. It's not the babblers, but the potential rapists and stalkers and weirdos-with-axes-to-grind that I most worry about.
That said, should I take the plunge and post an ad?
Are my self-defense skills really that good yet? Not sure.
Where's my faith in humanity?
Would I be having this sort of insecurity if I wasn't female? Unfair!