It does vary, sometimes it takes a few month and sometimes a few weeks. You can still do selections if you are studying that year, but that depends if you are willing to miss work for a few days. If you miss a semester test or something you can ask them to write a letter to the professor explaining your absence. I missed a test because of selections and my calculus prof was fine with the letter he received from them, its as good as excuse you can get...no arguing with a letter from the SAAF
If you already have the application form(you can get it off of this website) then you can send it in whenever. They keep your papers until they need it.
Basics for the pilot/navigators wont start for the groups doing selections that same year. As with my selections, they took a whole year doing selections and getting candidates and then in November/December they did the interviews and then started with basics sometime the following year.
I'm still deciding whether I should do selections again or not. I had a medical problem so I'm going to have to see a doctor first so that he can tell me if im better now or not, if I am I will send it as soon as possbile, probably some time in February, and then again in March.
The recruitment office...well go to the main gate(cant remember the street names), you will have to park outside...and then just walk through to the main building, you will see it, or otherwise ask for directions. Once you are in then just ask around there is some kind of a reception and I'm sure they will be glad to help you. But hand it in there, it will give you a good excuse to see what it looks like inside HQ.