What is connected to your input pins? If they are not actively pulled high or low by an external device, you will get random data.
You're checking for falling edges so I assume that the pin is normally high; so you can change
pinMode(2, INPUT); // DATA0 (INT0)
pinMode(3, INPUT); // DATA1 (INT1)
to
pinMode(2, INPUT_PULLUP); // DATA0 (INT0)
pinMode(3, INPUT_PULLUP); // DATA1 (INT1)
and see if that silves the problem.