Ambimb emails, and asks about finding a job as a public defender. In particular, is it a good idea to spend two summers at the same PD's office, and perhaps get to work on cases in more depth because you've spent more time there, or is it better to get experience at a different PD's office, because then you've seen the practice differs from place to place? (Ambimb, I hope this is pretty much the question you asked. Gmail isn't working as I write this.)
First, let me say, that in my eyes, a summer or two doing the work you want to do is the most important experience you can have on your resume. And it's important for your own peace of mind, knowing that this is actually what you want to do. Most PD's offices would take someone who has shown a consistent interest in the work over someone who hasn't (but, for example, has better grades or was on Law Review).
I think that it's really a good idea to stay at the same PD's office for two summers. Particularly if there's any chance that you want to get hired there after graduation. PD jobs are not that easy to come by, and you'd have a good foot in the door.
But, even if you aren't sure you would stay there after graduation, I still think it's a good idea to stay at the same place because of the experience you'll get. You stated that you'd get to work on cases in more depth and perhaps handle some cases in court. This is not something that you get to do everywhere (and be forewarned: it's a feature that some PD's offices advertise but don't deliver on - you go in thinking you'll be trying cases, and you end up carrying a senior attorney's briefcase all summer). Try to think back, do you remember seeing 2Ls actually handling cases last summer? I only mention this because I've worked in 2 offices, one where the summers really were handling cases, and another where I know they advertised the summer experience as "you'll be able to handle your own misdemeanor caseload" but no one actually did.
And even if you found another PD's office that actually allows 2Ls to practice, I think you might have an advantage in the PD's office that you've already worked in. Summers go by quick, and you can skip the meeting-everyone-and-getting-shown-around part, and get right into it.
I think the depth of experience is more valuable than the opportunity to view the variation in PD's offices. Yes, they'll be different throughout the country, but in my office we often have people transfer in from other cities and they adapt pretty quickly. Sure, they spend a few weeks asking, "Where's the fax machine?" and "Where is this courtroom?" But the more important thing is that they're hired because they can work with our client population and advocate for their client, and that's a skill that you can develop in any jurisdiction, but only with experience.
Finally, I saw in your comments that you were also considering a policy house. I think this could be a good experience, and surely would increase your knowledge of the law. Make sure you ask yourself, would sitting at a desk researching and writing all summer kill me? I know that it would've killed me. I think it would be better (both because it'd be more interesting and because it'd give you more experience) to get your feet wet in an actual courtroom with actual clients. If you end up taking the policy job, my advice would be to eventually take a position where you get experience with clients, either through a clinic or an internship during the semester.
Otherwise, it seems to me like you're leaning toward staying at the same PD's office, and I think it's a great idea. Let us know what you choose and how you enjoy it!