Leto is pronounced LEH-to in Croatian, and I believe the Greek pronunciation would be similar.
However, it's quite possible that it's lee-TO or lay-TO in in English (since many Greek names don't retain their original pronunciation in English).
ETA: I found this
http://www.forvo.com/search/leto/en/ which seems to indicate that it's lee-eh-to in English.
This message was edited 9/12/2012, 11:55 AM