The sample code is using your hardware serial port to talk binary to the range sensors. You can't also use the same hardware serial port to talk to the USB cable to the PC. That is why the output lines of the example are commented out:
I suspect you are out of luck unless the "I/O Expansion V5.0" provides another RS485 serial port on a different pair of pins. You can't move the USB connection to different pins without mangling your Arduino board.
You can use the NewSoftSerial library to talk to