Alright, sorry it took me a while to check into this.
So I have an easy solution... it's already built to handle this. All you have to do is add &testServer=east to the end of that URL. If you go to the speed test mirror page you can get the names for all of the servers from the 'set default' buttons. I didn't specifically design that to work with the auto test... but it does. It's all one large program, so that command flows right over to the auto test. Pretty cool, I didn't even have to do anything.