Horrible SAT proctor for the October 3, 2015 SAT. Should I cancel my SAT score?

I live in CA btw, by when should I mail my cancelation request for it to be received at:

1425 Lower Ferry Road
Ewing, NJ 08618

??

All the way in the east coast! I am unfamiliar with paper mail. How can I assure that it will be received by Wednesday 11:59pm?