I would personally take it at the beginning of Sept, because mid-Sept you might run into some first exams for your classes in the fall and you might have a mental breakdown if you have the PCAT and exams.
For VA and RC, I feel like it's just luck if you know it or not. Keep doing practice exams and make sure you really understand why you got the VA and RC questions wrong on the exam.
Also, if English is your 2nd language, I would focus more on the sciences for studying (be sure you do practice questions for VA and RC, but it would be a waste of time to try to memorize a vocabulary list when maybe 1 or 2 words will appear on the actual test). I've seen many people, myself included, score low on RC and VA, but do amazing in the sciences so it brings their composite up. Personally, I scored in the 40-50s for RC and VA, but got a 99 in chemistry and it brought my composite up to an 84.
Good luck!