mlshanks, do you have some deep rooted anger towards Olvera St? It is hardly as horrible as you are making it out to be.
Not sure what you mean by the "real Los Angeles treasures" but the last time I checked Chinatown was almost entirely Thai and Viet Namese nowadays. The "real" chinatown is in Alhambra. Also I have never seen "Hispanic merchants in bad Mexican folk costumes" on Olvera St. Mostly it is just working class Hispanic merchants selling bad trinkets. Pretty much the same stuff you see in Tijuana. There is the Avila Adobe, though, which is historically accurate and on Olvera St.
Other than your preference for sandwhiches over Mexican food, what does Phillipe's have to do with L.A. history any more than Las Golondrinas does? They have both been around for decades and are in downtown L.A. The staff at Phillipe's knows no more about L.A. than anyone else. The food is good, but that sort of depends on what you are in the mood for, doesn't it?
To the OP I would say to decide for yourself. The wikipedia link that mlshanks provided is a good one. Here is also another web site to look at for more accurate information on Olvera St.
http://www.olvera-street.com/