Would like help from any women who take a form of martial arts?

Well I have a problem on campus with guys sometimes being too........free. touchy. Sometimes blatant and other times they act like they're joking. Still, it gets annoying. I usually let them know verbally it's not welcome. But it still persists on occasion. A friend of mine who I talk to about this, suggested martial arts, saying it would be good to know in case it ever got really aggressive. She mentioned tae kwon do. Have any of you taken something like this before? Ever been in a situation where you've actually had to use it in the past? I just wonder how effective it would be on a bigger guy if one did get aggressive. Is taking this a good idea? I'd like to know your experiences and advice. Thanx.