I don't do DUI/criminal, but am in a small-ish (6 attorneys) plaintiff's personal injury firm. Law school was a generally unpleasant experience for me, but I love my job. I work 32-34 hours a week, like my co-workers, and was able to get a fair amount of responsibility from day one. I make a small salary by attorney standards, but the bonuses make up for it. There is, of course, a significant stigma attached with Plaintiff's PI, which was the main reason I never saw myself doing this when I was in college/law school, but that wasn't an issue upon meeting our clients and starting to work here. I got my job by virtue of meeting one of the partners while I was in high school and keeping in touch since then, so I certainly didn't need an outstanding law school resume, either.
All else aside, I think the best thing to do would be to stick it out for another semester, try to split your summer between two different types of law firms, and then make a determination on whether you like the actual practice or law enough to make a career out of of it. Of course, if it's going to be another $20k or so for that extra semester, that's a hefty price tag. If you do decide to quit, run in the opposite direction and never look back.