Can you be a faithful Christian and still dance? Yes. Nothing un-biblical about dancing.
Is dancing bad if you do it to Christian music? See above answer.
Is it okay to listen to worldly music even if it doesn't curse and doesn't have an inappropriate message? This depends on you and your conscience. Some people can't handle, or don't want to deal with secular music. Others don't seem much phased by it. If you feel there is something wrong in it, don't do it. Listening to it when you think there is something wrong with it Would be a sin. There is no right an wrong answer, though some will tell you there is.
Also is it okay if Christian girls where bikinis I see many strong Christian girls where bikinis and it doesn't affect their faith. *wear
And because something doesn't appear to affect their faith doesn't mean it isn't. Is it affecting their witness?