How and where does the ADP get it's source of air from? Directly from the engine bleed air?
From the bleed air manifold, so you can still use the ADP even if the associated engine is not running, or from the APU.
Remember these ADP's are demand pumps and only cut in when the EDP can not supply enough pressure, normally in high work load situations, gear/flaps etc etc.
since the AC motors are powered by EDPs (if I remember reading it this way!)?
I presume you are talking about the AC demand/aux pumps. EDP's running or not (Engine Driven Hydraulic Pump) has no bearing on AC generation at all.