St. Mango's, also known as St. Manga's, appears to be some sort Wizarding rehabilitation facility. It may be a typo of St. Mungo's from the books.
St. Mango's is a place to get treatment for Voldemortserum addiction - although Proffesor Sinister refused to go get treatment. St. Mango's also treats "pedofiles". At one point, there are plans to send Snap and Loopin there after they videotape Enoby in the bath.