The turn signal relay location on a 2003 Ford Mustang isn't a single, easily accessible component like in some older vehicles. The turn signal function is controlled by modules within the car's electrical system, rather than a standalone relay. You won't find a "turn signal relay" in the traditional sense. The functions are integrated into the Body Control Module (BCM).
Therefore, there's no single location to check. Troubleshooting turn signal issues on a 2003 Mustang requires diagnostics using a scan tool to check the BCM and related wiring for faults. A mechanic or automotive electrician would be needed to properly diagnose the problem.
