Most listings are in the $10's per square foot per year. The Orange County region is experiencing a a boost in rates. In the last 3 months, the median rate increased $15 per sqft per year.
In the last 90 days, 25 listings have been posted online, which means office spaces are probably going fast. You'll want to be prepared to tour spaces as quick as possible. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,030 sqft. Most buildings in this market were built in 1998 and are Class B.