As previous posters have pointed out in the YA I have encountered sex has not been glamorized. I do however think one of the important aspects of YA is to deal with the issues that real teens deal with, and sex is simply one of them. Not talking about it or only talking about abstinence is not going to change reality, I think that has been sufficiently proven at schools that teach abstinence only.
If you are however truthful about sex it will help teens more. Truthful means yes, also talking about STDs or pregnancy scares, but it also means being truthful that having sex as a teenager is okay and can be something nice if you take precautions and are ready. For most people their first time won't be the best sex of their live but it will be something nice they will not regret, something the experiences of previous posters demonstrate and which I also had. Some books will deal with the difficult aftermath of unprotected/too early sex while others will deal with it as a positive experience teens go through, and either way is valid.
For me the biggest problem is the notion of 'if you don't talk about it, it will go away' which just isn't true, as we all should know by now. Inversely, just because you talk about sex is not going to make teenagers jump up and do it immediately. I for one grew up very well informed about sex and my parents never said I should wait to a certain age/until marriage etc. and yet I actually waited to have sex longer than a lot of friends I knew who did have those parents that preached abstinence only. Why? Because I was taught sex was not some evil thing, that I should be okay with my body, which meant I also valued myself and waited until I was fully comfortable with having sex.
Jo, I understand your concerns but writing about sex does not mean it is immediately glamorizing it, it is simply helping teens with an issue they deal with in reality and helps to educate them about it.