Very interesting point peakguy. I had my first drink at a bar in New Orleans two years before I could legally drink anywhere else in the nation. At that time, New Orleans realized that the city economy would get more money from tourism sparked by a drinking age of 18 than they would get in federal highway funds. It's probably not a coincidence that New Orleans is a tight-knit, transit-friendly city like the ones you mentioned. (My next legal drink came two years later, at the stroke of midnight in New Carrollton, Maryland, aboard an Amtrak train taking me back to college.)
I had my first legal drink in Vienna, Austria at age 16 while on an exchange program and did not have another legal drink until my study abroad in Copenhagen at age 20. No comment on the period inbetween, but I remember many people testing their limits to alcohol in parking lots on Staten Island and at frat houses on campus...not exactly developing a healthy relationship with drinking or drinking and driving...

When I worked in Cambridge (UK), during my early 20s, I discovered a great British institution called "the local" - every little village, town, or general gathering of anymore than 10 houses seemed to have a local pub, somewhere that anyone in the surrounding area could walk or ride a bike to conveniently. In "the local" you would find an intergenerational group of people from the area that all knew each other, drank, talked, debated, argued/fought and learned to live with each other. People even brought their kids to talk to the old men and drank soda and juice. I thought it was one of the best parts of British culture, and as a side benefit this institution greatly reduces driving to go drinking.