I took the spring PDC at Occidental Art and Ecology in California. From what I gathered, it was among the more expensive (~$1600) but also the best rated course within my options, and the most information heavy on a long standing Permaculture community. I did my research ahead of time, and Im glad I did as Ive heard of plenty of money-grab type schemes flying the Permaculture flag.
While I have to acknowledge that it was hands down the best vacation I ever hope to take; 3 UNBELIEVABLE meals a day that were ~80% sourced from the campus, a solar powered hot tub and sauna, otherwordly gardens/backwoods free for wandering, and 5 star sleeping arrangements (or space for a tent, for the frugal hippies)... The academic aspect made my head spin.
It was a heavy course load for 2 weeks. 8-10 hours a day I believe. I generally do well in school and was arguably very well studied in nearly all Permie subjects presented (Thanks Paul!) - and I still found it an incredible glut of information with no shortage of experts to hassle with my specific, weird questions. Every night I poured over pages of notes and protips Id never heard before. There is no such thing as "knowing all the rules of Permaculture".
Just as important as the information was the community and fellowship. Im sure its always awkward to start a live-in course with a bunch of weirdos of all different ages and backgrounds - but by the end of the two weeks I had 30 new lifelong pals. Being in an environment with a few dozen people with no connection other than caring way too much about being decent humans and excellent earth stewards really struck me. One by one I realized everyone there had a heart of gold and was genuinely engaging to talk to - and Im a deeply crabby dude as far as 'most people' go. PDCs dont attract dunces or jerks. As a matter of fact, our 2 years reunion is in 48 hours, and a number of us are boarding planes and carpooling to ensure we get to meet up again. Permie Fam 4eva.
The teachers and residents of the property also top the charts for Heroes among men (and women!) - Even the interns were star spangled. Whenever things are going really poorly - I just close my eyes and envision my PDC!
TL;DR - Results may vary, but a well researched PDC is worth every penny. I and 30 other strangers had the time of our lives which provided no shortage of experience, information and fellowship for further Permacultural endeavors. While it seems expensive at the outset, the math works out pretty well on lodging/hot showers and 3 meals a day... even if you simply want to call it a vacation. Just as well, seeing Permaculture in action on a piece of land for 40+ years will really knock your socks off.