This time, I'm doing it to see how much better the world is for vegetarians, and to see how the diet change affects my metabolism, moods, etc. And because so very many of my friends, and one person I'm spending a lot of time with, are vegetarian and this makes it easier to eat out with them.
Short version: eating vegetarian in San Francisco is easy. Eating the same in popular chain restaurants is surprisingly difficult. Eating without meat in hotel/resort restaurants is nearly impossible. I'm eating mostly from the cooler in my room, with a grilled cheese sandwich here and there.
The real surprise, however, has been how quickly it has turned my stomach. This has been fairly shocking. I thought I'd be hungry for a steak or sausage by now, but instead they turn my stomach when I look at them. I didn't expect that. The choices part of staying away from meat has been much easier than I expected.