As others have implied, the amount of time you should wait before sex is exactly the time you feel you should wait. Or in other words, do it whenever you want to (but not before).

I can only speak for me personally, but if a woman did not want sex within the first month, I would likely move on since I would take that as an indication she isn't really interested in me. However, that is only useful information if you are planning on dating me, which is highly unlikely. Everyone is different.