This is a controversial issue you know. And like many have already said it is your personal choice.
In quilting I always wash before starching, cutting and sewing. The finish on the fabrics bothers my fingertips. Must be in whatever the manufacturers are putting on the fabrics to make them look even prettier.
I have friends who don't wash their fabrics prior to sewing so that when it is washed afterwards it shrinks giving it a nice quilty look.
I just read somewhere from a lady who makes her own starch that she always washes her fabric 'before' anything else. She starches so then she washes when the quilt is done. Not everyone does this.
Suggestion: for one whole quilt wash all of your fabric and then for the next one don't wash your fabric. Maybe start out with a doll size quilt. See how you like the feel of it when you are piecing it together and then how you like the looks of it afterward. Happy quilting.
:-D