To boot from sd-card in general: Power down, insert powered USB cable (connected top charger)
To boot into internal Cyanoboot: Try pressing and holding the "n" key right after you turn device on (from completely powered down)
I have absolutely no idea if this could be any help for you or not, but I have a really easy "half-cheating" way to do it that I describe under "C" in this post. I do not own a Mac though, so maybe nothing of this can be used there. But no harm in looking, I guess:
http://forum.xda-developers.com/show....php?t=2081981