I'm not saying I wouldn't have wanted one, but when I did the walk last time, I never had a map the entire time.. between the yellow arrows and others walking, plus locals along the way, you almost don't need one. Again, that's not to say you shouldn't have one if you can find a lightweight one.
I am known for being "directionally handicapped" among my friends, and I only got lost once on the Camino (and it was only for a mile or so). Itwas kind of funny - because I learned to rely on instinct and in this instance, I realized pretty quickly I was going the wrong way.
Good luck! You'll love it.
Susanne