I don't have any insights on whether pigma pen would work on batiks. However, I think you could easily mix batik fabric with non batik fabric to resolve this problem.
You could use non-batik fabric for the signature blocks, and batiks for the rest.
This quilt (
http://www.quiltingboard.com/picture...y-t262070.html) could easily have used batiks for all the colored fabrics.
I agree with Up4BigChal that I wouldn't want people to sign after the quilt is finished, in case of errors.
If you bring the signature fabric only, I have read that you should iron it onto freezer paper..... it stabilizes the fabric temporarily and makes it much easier to write on. I have also heard that it helps to draw an outer border so guests can sign inside the lines. That way, the signatures don't get caught in the seam allowance. (You could draw the border with a frixion pen, so you can make the lines disappear with heat after the guests are done.)
Good luck with whatever you decide!