Your definitely right on the abstinence message being unrealistic. No matter what you try teens are going to have sex. It's part of nature and our cylces, it's an age old instinct to say the least.
So you can tell them till your blue in the face not to have sex, but they will.
However, there is that huge problem of teen pregnancy then that comes along with this.
It seems to me the best thing we could do is for parents to open the lines of communication. Ensure that your child is not going to be to embaressed or afraid of getting into trouble to talk to you. Because then if they think they can't go to you for all those intimate details and questions(no matter how horrowing an experience it may be for the parent) they then go to peers and get all the facts jumbled up.

Well I feel like i've just repeated what everyone else has been saying
Oh well , not deleting all this