I think the most important thing is knowing your own status before getting involved in a relationship, this way you will have something to discuss. That's not to say the subject about safe sex should not be discussed.
A person should not hesitate to find this out immediately. My answer is in response to this, because i knew a woman that would go out with men, never telling them "up front" that she had the HIV until a later time. Of course if questioned, she would usually tell the truth.