The only safe sex is no sex!
80% of all people have intercourse at least once by the age of 20. Roughly 60% of teens in the US are sexually active. So information about how to prevent pregnancy and disease is crucial for young people. Having this information does no harm to people that aren't having sex and promoting abstinance can't be the onlly solution.
There is no published study of an abstinence-only sex education program that demonstrates that these programs help young people change their behavior. On the other hand, programs that include information about contraception have been proven to actually postpone intercourse. Most importantly, all young people -- those who are sexually active as well as those who wait until marriage to have sex -- have a need for, and a right to, accurate, frank and positive information about sex.