Not cheating, but apparently cursing in English or Spanish will cost you the match...this Perez kid defaulted in FLA after letting a few colorful words fly.
From Zoo Tennis (I condensed link to full below):
At Salvadore Park, where the quarterfinals and semifinals were played today in the boys 18s and boys 14s division, top seed Christian Langmo got the most unusual win of his tennis career in the semifinals, when his opponent, unseeded Alfredo Perez, was defaulted from the match at 3-3 deuce in the third set.
Perez was defaulted for his third audible obscenity in the match, the first two coming in the last game of the first set when he was serving trailing 3-5.....At 3-5, 0-30, after a Langmo winner, Perez yelled out "he's playing out of his f***ing mind" and a roving umpire gave him a point penalty..........
The third set continued with both boys playing well and holding serve until, at 3-3, Perez let a 40-15 lead get away. When he failed to win a third game point, he shouted that he was playing like the Spanish word for excrement. The assistant referee checked with her Spanish-speaking colleague to make sure she had heard it correctly, and called both boys to the net, where she awarded the match to Langmo. Langmo shook Perez's hand, then Perez tossed his racquet in the direction of his bag and after a few seconds sat down and loudly said the same word again. Because he was defaulted for misconduct, the 15-year-old from Coral Gables was not allowed to play his doubles match later in the day.
Whole story is here: