I have not eaten Mexican oysters in Mexico, but I used to buy bags of oysters from Mi Puebla, a mexican grocery chain in California. The oysters were produced from Ensenada, near Tijuana. I ate those oysters (week old) raw, and no stomach issues.
I am not making a blanket statement to say that eating oysters raw from warmer waters are ok. I am just offering up a data point. Now of course, the thought of warm water near Ensenada did cross my mind when I ate them.
