Are they good-looking or nice? If they're ugly and/or mean, don't go!
But regardless, if you're friends, go! You will rise in the ranks of the ladies. You never have to tell any of your friends that you were bored enough to hang out around a convention devoted to Japanese animation.
Plus, okay, take pictures. There are two kinds of pictures you might want to take: pictures of people who dress up well, because those are cool, and maybe pictures of people who dress poorly, so you can laugh about it.
Of course, I encountered many, many of the latter while I'm there. My (then not) ex took pictures of pretty people. I think there were a total, of, what, like, ten? Then again, this was Anime Expo. Who knows, maybe everybody's a Southern belle.