The PA mechanic says that it is safe. Would it be better to have the problem fixed in PA or FL? Funds are limited. Only 44,865 miles! Warranty conveniently expired prior to problem about two years ago. Until now, driven for pleasure only. Thank you for your help! (Moving to FL)

Yes, you can drive it. The check engine light will remain on and you won't have torque converter lock-up, but you can drive it.
Cadillac has a bulletin: Bulletin No.: 04-07-30-034A
That bulletin lists the parts that are required to provide an effective reliable repair. Nothing short of this will truly fix your problem.
Make certain that the diagnostic leads to that repair. If the problem is actually the Powertrain Control Module (PCM), that bulletin won't help but you can still drive the car.
Be advised: without torque converter lock-up, your going to be running the engine at a higher RPM and shouldn't expect the same fuel economy as before.