Think of it as elements if for beginners, and CS is for anything above that.
If you're going to start getting in to graphics, just go with CS and never touch elements.
There's nothing at all wrong with CS2 other than some files aren't guaranteed to convert backwards, like features introduced in the later versions.
I use CS5, but I wouldn't be opposed to using CS2 on another computer, they really aren't that different.

OH golly gosh, I wouldn't recommend purchasing the latest version, everyone knows Adobe pump hundreds of thousands of dollars into making inferior products every year!

This post was edited by CHurley on Jan 29 2013 06:43am

If you want to go free, just get GIMP. Plenty of tutorials available on youtube, and that's more graphics power than you need if you can't even answer this question, yourself.