Most listings are in the $30's per square foot per year. The Carlsbad region is going through a decline in rates. In the last 3 months, the median rate fell $5 per sqft per year. That's a 13% decrease in rent.
Compared to the rest of the San Diego market, the Carlsbad submarket has less expensive rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 68 listings have been made available, so you'll want to check back regularly for new listings. About 6% of the available space in the Carlsbad are subleases, so you will probably have to focus your search on direct office leases. 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 2,400 sqft. Most properties in this market are close to 2 stories. Most buildings in this market were built in 1998 and are Class B.