Most listings are in the $40's per square foot per year. The Coronado submarket is going through a an increase in rates. In the last 3 months, the median rate rose $48 per sqft per year.
Compared to the rest of the San Diego market, the Coronado region has more expensive rates, and you'll need to pay a premium to be in this hot region.
In the last 90 days, 2 listings have come on the market, which means leases are probably going fast. You'll want to be prepared to make an offer immediately. About 200% of the available leases in the Coronado are subleases, so you might be able to sign a shorter term by taking over a previous lease. 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 680 sqft. Most buildings in this market are around 3 stories. Most buildings in this area were built in 1991 and are Class B.