Building a green home is possible anywhere in California (and anywhere in the world!) with the right mindset. A good reference for planning your home's location and site design is the book Your Green Home, by Alex Wilson.
Mendocino County provides many opportunities to benefit from green building strategies. When building in Mendocino County, as in most rural counties in California, the homeowner should first consider access to fresh drinking water (most often from a well), soil conditions for septic systems (water percolation rates), and fire safety zones around the building area. The Mendocino County website provides an overview of the permit process from start to finish. Other considerations include zoning, privacy, views, available building sites, solar orientation, microclimates, wind and rain patterns, sub-surface soil conditions, site access during construction, and native vegetation.
The Mendocino County permit process has one unique area of green building opportunity called a "Class K Limited Density Rural Dwelling Permit." This code section allows a less stringent standard for property owners building their own homes who wish to use alternative methods of construction. It "allows for more flexibility in size and human comfort conditions." That means your home could include some advanced green technologies not currently accepted under the California Building Code, including natural building systems, rainwater harvesting and greywater reuse, composting toilets, and foundation-minimizing structural systems.
For more information:
You'll find a comprehensive overview of site considerations by Michael G. Smith, author of The Art of Natural Building, on the Oikos website.