No, Iguanas don't have a voicebox.

If they DO make any sort of verbalization it means they are REALLY in some sort of distress or pain. An open mouth hiss is about it.

Usually if they want something they just become a big PEST. Try climbing all over you or licking some part of your anatomy and start sneezing all over you. That usually means they need to go in the tub to Poop or they are hungry.