Compared to the rest of the Bay Area market, the Sonoma region has higher rates, and you'll need to pay a premium to be in this hot region.
In the last 90 days, 19 listings have come on the market, which means leases most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 940 sqft. Most properties in this market are approximately 2 floors. Most buildings in this area were built in 1978 and are Class C.