Would a bad ignition lock cylinder prevent you from shifting out of 'Park' in a 1995 Mercury Sable?

If you can turn your steering wheel with the key on, then more than likely your brake sensing switch is bad. This switch senses the brake pedal being pushed down,..which must be done on these models in order to shift out of park. The brake shift interlock feature prevents the vehicle from being shifted from park unless the brake pedal is depressed.