As long as you can kind of touch the ground you'll be fine... Try to borrow some kids bike so your feet touch the ground from the seat, sit on it, then push yourself along with your feet and occasionally lift them off the ground and roll with the momentum.. Eventually you'll feel comfortable with moving and not having to touch the ground/staying balanced.. Then you can whack your feet onto the peddals and really get moving...
You could even try starting on a sloping hill, so you can just push yourself a little bit with your feet, then lift them up and let the hill roll you down... (familiarize yourself with the brake before doing this )

If you end up going with Pac's idea and using training wheels, please please please take photos for us!!