Recording calls is specifically disabled due to legal issues. You can get an SGS phone to have the capability, but it requires loading a custom ROM derived from an Android release in a part of the world where it is NOT illegal to do so. Yes yes, I know if you tell the other party you are recording it is ok, that is not the point. The point is, the software is NOT there because it is illegal and they clearly do not trust us to not lie about it.
Anyway, I would guess there is a similar situation for the SGS 2, but you are best directing the question to that forum to ask for a custom ROM that supports call recording. There is no way to get it without learning how to do it yourself, that I am aware of.