Totally bring it... I told all my students to bring one if they wanted to. I mean, one of the main joys of flying is to be able to see things you can't normally see, so you may as well capture the moment. I have a small little point and shoot that I keep in my flight bag. Sometimes when I see something neat I will whip it out and capture the moment if it doesn't dirupt what I am trying to do for the student. I also took photos of my guys during their first solo which they really appreciated.
Most important thing though: if you are the student, that CFI works for you. If you want to do some turns around a point over something and take photos, he should be fine with that, if not, find another. Just because you are not the PIC does not mean that you are not the boss!
Have fun!