Add it right away, adsense wont ban your account for lack of traffic. You just wont get paid a lot. As always, you should review the latest Adsense TOS to make sure your site is in compliance.

I don't see a problem with adding Adsense early, provided you have at least some good content and your site meets Adsense guidelines. I don't think they really care about low traffic as long as the site is of good quality.

Usually I tend to add adsense when I hit at least page 2-3 for my keywords. If you are making your first request make sure your site is at least 3-4 weeks old with at least 4-5 pages with original and decent looking content.

2.15pm is the best.

Adsense will never ban your account because of little traffic. You will not get good revenue that's all. When you are happy with the number of traffic, then you could add the code.

If you already have adsense account you could implement it right away there is no need to wait until your site grows.