All classically trained musicians learn to read music, but singers have to be able to turn this into notes(doh rah me fa soh la Te doh) without using the physical manipulation of the instrument as a guide. This is a tough skill that needs lots of practice and dedication, but you do not need perfect pitch to accomplish this. Make sure you have the fundamentals covered (which involves knowledge of tonic sofa notation,lines and spaces of a music staff,rhythm etc), and keep practicing every day, and eventually you'll be able to sing pieces without any advance preparation.
This will be in several steps. sit back and enjoy.
