sorry man but thats just BULL! :Total-CP: :Total-CP:
The Mustang has a temperature gage does it not, plus a coolant warning light if it exceeds a particular temperature.
If you had a hose burst (which is fairly common on all cars) you would have no extra warning.
Yes if the entire belt broke you'd probably notice other things, such as the tacho would probably stop working (has a pulse feed from the alternator). But the battery would certainly run the car long enough to over heat it.
I had an alternator failure on my Discovery will on compeition (night navigation course on & off road), I drove for 3 hours over roads and off road sections at night with the lights and stereo on. The battery only went flat once I got home.