Pros
The Austin office has experts from a variety of backgrounds, including biology, engineering, economics, business, geology, and law. The office is very laid back (especially in the summer, I'm told) and work hours are flexible. Once you demonstrate that you are a serious employee, there are great opportunities to take on a prominent role in research. I was able to attend City Council hearings and meetings with other environmental groups, and my research was regularly used on official EDF business. Best of all, nearly everyone is friendly and engaging. I developed several valuable connections that have lead to promising job prospects--and not just in Austin. Highly recommended (especially at $12/hour)!
Cons
As a motivated and passionate person, the office was sometimes too laid back for my tastes. I found myself doing more work than some of my "bosses" on some occasions--not because I was told to work harder, but because they weren't as dedicated to producing results as myself. Also, make sure you actively try to seek out work that interests you. When I first arrived, they would have been more than happy to give me somewhat brainless tasks to be completed in my little office for the duration of the summer. But because I pushed and nagged until I got work that was engaging, they were more than happy to comply. I got the sense that the full-time employees didn't trust interns to be effective and dedicated, but once I proved to them that I was capable, they shoveled over a great deal of responsibility.