Since we teachers only get 26 minutes for lunch and our cars are parked literally 1/4 of a mile away from our classrooms, leaving for lunch isn't even an option. However, we don't eat at our desks -- we share lunch in the staff room. Once a week (rotating schedule) someone brings lunch for everyone, and we all look forward to that. I definitely enjoy that sliver of time with adults every day.
However, I will add this, though it seems against the grain: You should pay attention to the social aspect of lunch and be sure you're "playing" at a minimal level at least. In some companies, a lot of not-so-obvious office politics go on during lunch, and if you NEVER go out with the group, you can be seen as a person who doesn't care to interact positively with the group. It's like this at my husband's office. He likes to come home for lunch or take a walk, but he is careful to "go out with the guys" often enough to stay in the loop.