Several species target Acropora for certain. I suppose there isn't really as much of an issue with more noxious soft corals and mushrooms, as I've kept them together before, actually. I think if you look up diet under A. nigropunctatus (and at least one other, if I remember correctly) at Fishbase, you should find those references. Beyond that, I've watched them do it--I introduced some practically dead pieces (mostly ones that were stn'ing). The puffers loved it.
I tried a porcupine in my first reef tank but it very quickly outgrew that tank and had to go back within a couple months. Since then I have learned a lot more on "proper homes" for puffers and have since felt I do not have the required tank sizes to make them happy so no more porcupines for me for the foreseeable future. 
