http://chihoe.com/to-bone-or-not-to-b... for more info! YES guys, it's ok to get hard when you dance.Some guys can control it and some can't. BE COMFORTABLE with your body. Why be ashamed, being apologetic is not going to get you any points with women.
If they are dancing that close with you they already have some level of comfort with you, so grind as nasty as you want. I know it feels good but occasionally push them off so you don't seem needy.