"practice rigorous honesty -- and to emphasize that you are an individual not representing the fellowship as a whole."
I'll second that. I would find your position to be rather difficult. Try to state the facts. If the guy is on his fith DUI, his commitment seems sketchy, and you've only know him a few weeks, his prognosis doesn't seem great by any statistical measure. You know the facts better than we do. Communicate them as effectively and honestly as you can. I would write a letter abstaining from anything other than mentioning the number of meetings attended if you are unsure of where this person is really at. Court mandated aa has always confused me as there are other options that are effective, and it is not nesc the best for someone even if they are sincere in changing. To thine ownself be true.