Hi, it really depends on your preference. It's been suggested in research I've seen that most people tend to look to the left side of the page first - probably why Google recommends using the left side for Adsense. You just have to decide if adsense is more important than navigation.
You can go on either side in Joomla, set your menu positions and sidebars in Gantry or adjust your module positions to suit your needs.
The difficult we do immediately, the impossible takes a little longer.