I think it all depends on how fully committed they are to Buddhism.
I've studied about Buddhism for a few years but before I became very serious about it, I had issues with drugs, alcohol, depression and self-harm.
I have to admit, I have seen a few alcoholic Buddhists myself, too. One of my pen pals was a Buddhist and he would e-mail me daily drunk, lol.
Also, I noticed in the 'Smilies' there is a 'Happy' emoticon with to people bashing their beer mugs together as in to say "cheers" but most Buddhists are forbidden from being intoxicated.
The Buddha himself is no God, Buddhism is a teaching of spirituality and is not really a religion but a state of mind of awareness and peace, hence why most students of the Buddha-Dhamma suggest to stay clear from cigarettes, alcohol and illegal substances as this leads to suffering and misery.
Years and years ago, way before I began studying Buddhism, I used to drink a lot and was what some would call a "happy drunk" but as I got older, I became aggressive, violent, moody, depressed and suicidal. Buddhism is a great teaching because it leads a healthy, happy lifestyle, many Buddhists have stated themselves that Buddhism or 'Buddha-Dhamma' has changed their lifestyle completely. Meditation is known to decrease blood pressure and cure stress & anxiety.
I suffer from both anxiety and depression and I also struggle with self-harm. Buddhism has helped my state of mind in many ways that some people will never believe. Even registering here has made me happy, meeting people like David N. Snyder, Ben, cooran etc. has been extremely delightful.
I generally think alcohol is a bad choice in life. It destroyed my youth and destroyed the relationship with my mother.
"Do not dwell in the past, do not dream of the future, concentrate the mind on the present moment." ~ Siddhārtha, Gautama Buddha