This was answered on another forum. I've done this hundreds of times. Just squeeze the cable toward the riser. This will rotate the cam enough for you to get at the "hidden" screw. If you can't hold the cable while you do this then you can back the limb bolts out about 5 turns each and then do it.
Don't worry. The limbs won't pop off. You can actually back them out far enough to get the string/cable off the bow or completely disassemble the bow. That being about 12 turns.