The typical asking rate per listing is in the $20's per square foot per year. The Orange region is going through a a boost in rates. In the last 3 months, the median rate rose $2 per sqft per year. That's a 8% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Orange submarket has less expensive rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 64 listings have been posted online, so you'll want to check back regularly for new listings. 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 2,090 sqft. Most properties in this market are around 2 floors. Most buildings in this area were built in 1980 and are Class B.