Spanish in St. Louis

Last summer me and my family went down to St. Louis to visit my cousins. One day we went shopping for my cousins birthday present. After we got it we went to check out and there were spanish speaking people already there in line. I think they were talking about something like having a fiesta for their kid but i couldn't quite catch on they were talking so fast. When they finally checked out i was so confused but its a lot better than I would have been at the beginning of the year.