I know very little about permaculture. What I assumed was it was a farming method designed for scalable application. Elsewhere I heard these practices referred to in a gardening context, and I was quite surprised.
I checked Wikipedia, and the summary was a little too airy for me. I also browsed some aspects of the entry and came back to my original conclusion: this is all for someone who's got an acre or two.
Does permaculture have any revelance for anyone with, say, a community garden or backyard environment available?
When Bill Mollison first developed the permaculture concept, he was working primarily in Australia, where, especially then, there were far more small farms than in the US. So many of the ideas were first worked out at farm scale. But most of the people who refined these ideas lived in cities and suburbs, and so a lot of concepts and techniques were applied at much smaller scale. Most of the books on permaculture, other than Mollison's, are focused on homeowners and those with less than an acre of land (often far less). My own book is for people with 1/4 acre or less. The principles scale down (or up) very well; ideas like "design from patterns to details," "catch and store energy and materials" or "each part should serve multiple functions" all work at any scale. You just change the techniques and strategies used. And many specific techniques, like keyhole beds, herb spirals, and guilds, are geared toward the small yard. So it's very useful for small yards and community gardens.
One of the most powerful ideas is that of zones: Zone 1 is the area very close to the house (or whatever the center is), which holds the things you use every day. So for anyone, farmer or urbanite, that will be a social space, salad bed, herbs, water source, maybe compost and chickens, etc. It might be a 20-foot space around the house, and along the most-used paths. Then zone 2 holds things we use a couple times a week: fruittrees, production garden beds, cut flowers, tool shed, and so on. Larger properties have zones 3 and 4 as well, but city lots usually stop at zone 2. The inner zones are intensively gardened, heavily mulched--they are just dense with activity. Farms deal mostly with outer zones, residences with inner ones. So scale is to some degree a question of which zones you focus your energy on. A farmer will spend all day in zones 3-4. For a city person, zones 3-4 are where you work and shop and meet friends.