JOEL - It is not "bad" to date a non-member. LDS who have a good strong testimony can often be a good influence to a non-member friend, which can eventually result in their conversion to the Church. This type of situation however, is usually limited to the more mature adult members. Teenagers who are not quite as mature or strong in the faith may tend to be more influenced by the non-member friend. For teenagers under 18, it is the responsibility of the parents to approve of who their children should be allowed to date.
Because dating is a preparation for marriage, it is important to date only those who have standards and similar values as you do. When you are with them you should be able to comfortably maintain the standards of the Gospel. They should respect and support your desire to do that. Obviously if your goal is Temple marrriage, you will have to date someone who is a member or who eventually becomes a member before you are married.