Any new results?
About your concern on how efficient is the communication that you are using, serial communication is not the fastest communication, so it takes a while to send to your Arduino, process it in the Arduino, send it again to the Galileo and process it again, as a result we are going to have an important delay and of course you are not be able to see data in real-time. That's why I suggested you to take out the Arduino Board and only use the Galileo Board.
But I'm still having some questions:
1. How are you measuring the delay, and how long it is?
2. What is the reason that you are using the Arduino Board instead of the Galileo Board, is about libraries in the IDE?