The only caveat I would have is where you said 'God gave us all plants to enjoy'. That was said before the Fall and since then he put a curse on the ground and we do have various poisonous plants.
I dated Mary Jane for 7 years and it truly poisoned my thinking at that time, especially with paranoia and a scattered brain where I couldn't hold a conversation for over 30 secs in my everyday life.
Well if it does that to you then I would agree that you shouldn't do it, especially if that's what the Spirit lead you to do. The Spirit has lead me to change quite a few things concerning this matter, but it does not affect me the way you just described it does you. As a matter of fact I am pretty sure you couldn't even tell if I was high or not (not that that's my whole case, or even my only justification). That's kind of what I meant when I was talking about how it effected me at the point of my regeneration. It doesn't effect me like that, if it did I would more than likely feel different about it. I think that if you feel the Spirit telling you it's wrong for you then it is, but that's just not the way I have been lead to feel about it. Again I'm not saying my view won't change at some point, it already has changed a lot in the last 13 months, but right now I don't feel I am rebelling against God, or even not heeding His direction. And once again I am not saying this can be applied to anyone else, but as far as my own personal view on this subject, I feel for me it's not a sinful act. That being said if it did still affect me the same way it did in high school, I may not feel the same way.