Cable ties are always a good idea. If TSA has to check your bags, they will cut the cable ties off and then replace them when they are done.
Just remember to always at LEAST use cable ties, do not leave your bags unsecure. It's not for security reasons (if someone really wants in your bag, a luggage lock will not stop them, perhaps deter them but if they really want in there, they will find a way) but for another important reason:
so that your suitcases don't open accidentally. Trust me, it happens a LOT! I worked at the airport for 2 years and I saw many instances of things falling out of suitcases! Once I even saw undies go flying out of a suitcases on the ramp on it's way to the plane! How embarrasing!
If you are flying into the U.S. and DO NOT have a stop-over of more than 6 hours, TSA will not scan your bags. (There a exceptions but very few!)
If you are flying out of the U.S. ALL checked bags will be scanned by the TSA. Some airports do it in front of you, such as MCO but some do it after you check your bags in. If your locks are built in to your suitcase, ask when you check in where the TSA scan is done. If you have to bring your bags to an area, then keep them locked and if they need it open, you can do it then. If the check-in agent takes your bags immediately, that means you will need to have them unlocked. If that's the case, use cable ties on your zippers!