If you're just looking to just be able to pick-up a girl and not freak out when she says "hey, lets dance." I wouldn't look into beggining hip-hop classes as those are really just aerobic classes (very lame).

Download the popular dance songs you like (as the difference between club music and mainstream radio is none) and grab a full body mirror. Then imitate dancers on the music videos or youtube some of the hip hop dancers there. After a while you'll develope your own style but until then, don't start inventing ugly shapes and angles but rather get the basics. It helps to dress the part as well (baggy clothes) because hip-hop is about the confidence and swager one shows while dancing it. If you're practicing in a tied dye shirt, fannel and short shorts... you get the picture.

In the end, have fun with the music be remember: it's dark and she's going to be drunk. It's just grind and bump at this stage.