Are you suggesting the other side is completely ignorant of what those play signals mean? I suspect they pay a good deal of attention to them, if they would use steroids to win, they'd decode hand signals to win.
So, you have no problem with non-verbal communication on the field. Also, no problem with English being spoken on the field. OK.
But you have a problem with Spanish being spoken.
Interesting.
Ummmm....That's part of the game of baseball.
Both teams have signals.
Both teams try to "steal" the other team's signals.
Both teams change their signals as often as needed to try to keep them secret.
It's the same thing in footbal when the quarteback calls out "audibles" to change the play at the line of scrimmage. When he calls out "Thirty two, Twenty nine, etc.", it may be a signal to do something or it may mean nothing at all.