Hey Simon,
This is one of the fruits we decorate for Tet (Vietnamese new year- same time as Chinese New Year). I think what the other person meant to tell you was “this is a Vietnamese watermelon variety that was grown in Mexico.” They plant and harvest around this time for Tet.
There’s a lunar festival celebration this Friday-Sunday at the Mira Mesa park. Don’t forget to come out to enjoy the food, music, and games for those in San Diego.