Follow up the fax with a phone call. Journalists are often frantically busy. In the process the conference organisers gain an insight into what the media thinks are the best stories. They need to be at the phone numbers you gave to the media, at the times you said they would be available. Think of equipping them with a pager or a mobile phone, so you can locate them easily during the Conference.
Media needs pictures, but conferences are visually dull.
See if you can organise interviews in an interesting location nearby, such as a laboratory or a research site. Or make available some typical and exciting equipment at the Conference site. This will help TV cameramen and newspaper photographers make a better story. Or you could provide TV stations with broadcast-quality footage shot on Betacam tape, pictures which are typical and illustrative of the science under discussion. Five minutes is plenty.