Yes. A friend and I drove to Missouri and Iowa last year to check out Kirksville and DMU D.O. schools. We had a tour scheduled at Iowa but just showed up a Kirksville. Both were very helpful experiences. We talked to random faculty, staff, and students and I feel that this let us get a full and honest picture of the quality of those schools.
I checked out Chicago schools and the UW before I applied - I either arranged something with the admission's office, students that I knew, or just cruised around on my own. I found it very helpful in getting an idea of the places and eventually, in interviews when they asked the 'why here?' question.
If you can swing a trip without incurirng too much cost, I don't see why you wouldn't want to check out schools. It's definitely much less stressful than trying to get a feel for the school on your interview day when you are also nervous and trying to impress. Also, if you can say you've visited the school before the interview, it shows that you're serious about the place.
I took a self-guided tour of Penn over a year ago when I was visiting a friend who was in undergrad there. I really liked what I saw...funny, Penn is one of the handful of schools that rejected me without interview...oh well.