Since cannabis use is illegal in the UK I would say you are no more likely to be allowed to promote it any more than you would be allowed to promote handguns or heroin, at the very least you would be done for breach of the peace as you would have a hostile anti cannabis mob shouting abuse at you. All in all it would be a very bad idea.
Having read one of your previous posts then it would be a very good idea to keep a low profile in your home town for a wee while, handing out leaflets is not low profile

Cheers

NCM