Havre de Grace the a is pronounced more like the ah you would do at the doctor's office... aaaaaaaaaaaaaaaaah in both Havre and Grace... but that's my take on the French name. All bets are off because of the way Americans like to pronounce French words.. ie Hermès!
My Merlin kin always said "Hawv da Gra" (the R in 'Havre' being mostly silent) but they were from Ann Arundel County by way of Pennsylvania so there ya go, Hon. I've also heard "Hawv de Graw."
I think the general butchering of the original French resulting in a variety of pronunciations of the town's name is accepted as a funny regional oddity. I don't think there IS a "correct" way to say it!
As for the 2012 Horse of the Year? Everyone I know just calls her "the filly" at times so it avoids any mishaps!
Well since she is supposed to be named as the town in MD and that town is right up the road from me I would think the locals get to dictate the pronunciation however incorrect it may be. Just like I am from Duh Moynes and not Dez Playnes (Des Moines and Des Plaines)