Alcohol is probably much worse than weed or coffee over the long run. It's exceedingly hard to slowly poison your liver and brain over the course of a lifetime by smoking herb. It's easier than you think to do it drinking alcohol.
I'm not a teetotaler by any means. I drink a couple of glasses of something pretty much every other day. But that's about the limit of what a healthy, adult male should be drinking. Any more than that, especially over the long run, and you're setting loose a lot of chickens that will come home to roost when you're older.
I don't smoke weed with nearly the frequency I did when I was young. That's got less to do with my beliefs about its health effects, and more to do with being too busy. But every now and then, sure. Sharing a couple of beers and a joint is a fantastic social experience.
On a related note: SF is one of the most weed-friendly towns I've ever lived in, and there is virtually no stigma whatsoever here. One time I saw a dude light up right outside the freaking airport baggage claim, in broad daylight, and nobody around him seemed to care.