Was he actually sleeping with the prostitute, or simply having sex with her?
Check out the site, it seems to have testimony from one of the girls:
http://fedsinvestigationonsenmenendez.wordpress.com/
She said she met him several times and gives the dates (which should be verifiable with flight logs and what not) she said she was 16 at the time and one meeting was around her 17th birthday
First, there’s nothing illegal here. He didn’t violate any US law that I can see.
Now, if you can identify the news organizations that knew about this and just wouldn’t tell the story....that might be news. I’d like to hear about which media groups just dropped the story.