Personally, I disagree with proposing decriminalization for economic reasons, if marijuana was indeed dangerous and created societal decay than economic reasons would not justify the decriminalization. I think what we have to recognize is not that we are at a point where we need the revenue so badly we'll do anything, but that the criminalization of marijuana was wrong from the beginning.
Yes decriminalization would bring in revenue, but honestly that's not far enough, we need to legalize. Instead of trying to find creative ways to fund our city through the persecution of its citizens, for something we've all but admitted is not actually the problem it has been made out to be, we should work toward more just laws that don't criminalize the innocent.
Besides, legalizing marijuana would likely bring in even more revenue through taxation of clinics and sales, and would save money by greatly reducing spending on law enforcement and prosecution of crime linked to the underground market for drugs.