After re reading your original post again it seems confusing to me......
The child safety locks keeps rear seat passengers from opening the rear doors.
It doesn't keep rear seat passengers from being able to lock or unlock the doors ( even though they can't ). I'm not sure if the door lock buttons on the rear door panel become imobilized when the child safety locks are engaged.
When you say the driver or front passenger has to " unlock " the doors for the backseat passengers, do you mean physically open the rear door for them ? or Unlock the door using the power door lock button up front so the back seat passenger can open the rear door themselves.
Are your rear doors locked right now so that the passengers are trapped?
I have a friend that has a 92 Century, I'll ask him if his has the child safety locks & where they are located.
One other thought I had was if your not the original owner of the vehicle, a previous owner might of covered over the holes where the switches are with body puty & repainted the inside of the door jamb.
Previous owners do some strange things to their cars not thinking other people may own the car ten years later.
========= Harryface =========
1991 Pontiac Bonneville LE 3800 V6 ( C ), Black/Slate Grey _~_~_~287,629 miles_~_~_
~_~_~_~_U.S.A._~_~_~_~_~_
~~~The Former Fleet ~~~
89 Cavalier Z 24 convertible
78 Holiday 88 coupe
68 LeSabre convertible
73 Impala sedan