I started on coffee (mochas, actually) when I was about 9. They were a treat, not an all day, every day sort of beverage. I think I started drinking regular coffee in high school. I was also raised in Washington state with espresso shacks on every street corner, so that could have some bearing.
I jokingly tell my husband that we won't start the older munchkin on coffee until he's at least 3, but I'm honestly going to delay it for as long as is feasible. We don't have a coffee pot in the house, I keep my Keurig at work. I also don't go out for fancy schmancy coffee on a regular basis because it costs double here what it did in WA. If I do happen to get one and will be consuming it where kiddo can see me, he gets a chocolate milk type beverage instead. I wish I'd delayed the chocolate thing longer, I've created a (very cute) monster.