If the steering wheel isn't locked then unpluging the harness will work. Even if it is unlocked you run the risk of it locking up while driving!!! If the key switch pops out it will lock the steering wheel in whatever position you happen to be in. A safe way is to remove the whole ignition switch
http://www.pelicanparts.com/techarticles/Mult_Steering_Wheel/Mult_Steering_Wheel.htm
and
http://www.pelicanparts.com/techarticles/914_ignition_switch/914_ignition_switch.htm and then hotwire it. Iknow you don't want to go through the hassle but it is the safest way. BTW if the steering wheel IS locked you are out of luck, the locksmith is the only option.
Sometimes a key from another Porsche will work, try "raking" it in and out of the lock while turning lightly.