Can you still take subject tests in october if you are applying ED somewhere?
Sure, unless the college states that they will not accept October scores. But since scores should be available the 3rd week of October, there should not be an issue.
Every college I am aware of that actually requires or recommends subject tests and has ED accepts through the October tests. Some of them also accept November tests for ED.
Both of my kids took the October subject tests. My son applied ED, and the school accepted the scores, but not my son! 
I know of one girl who took her one and only SAT in October and still got into her ED school.