I entered a quilt into the county fair last year and I didn't wash mine. I wanted it to be flat.
I'm not sure all what they were looking for, but definitely make sure there aren't any stray threads or lint - I lint-rollered mine before I brought it but the lady I was turning the quilt into had me step aside and pick over it again because she spied a couple of threads I had missed. (Which was really nice of her to point out to me!)
When I got my quilt back, (and I won a 4th place ribbon!), the notes they gave me were very general. They liked my use of color the most. They had also jotted down the dimensions of the quilt and noted that it was squared up properly so that must be one of the things they check for.
I was entering in the "novice" category though. They might be a lot more picky if you enter in the "experienced" category (assuming your fair has similar divisions...)
Good luck!!!