IELTS is a requirement for all overseas applicants. Exemptions are those who got their secondary and tertiary schooling in english-speaking countries (USA, UK, Ireland, Canada, NZ).
Registration times actually vary from state to state. There are states that are receiving more applications than the other. And also, depending on AHPRA's assessment, they may require you to undergo a bridging program, which takes months to complete.
You may also refer to this active thread: http://allnurses.com/international-nursing/new-grad-filipino-501897.html
most, if not all, posts are from Filipinos but you may find it really helpful.