Compared to the rest of the San Diego market, the National City region has less expensive rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 14 listings have come on the market, which means office spaces most likley are leasing quickly. You'll want to be prepared to make an offer immediately. 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 830 sqft. Most properties in this area are around 3 floors. Most buildings in this region were built in 1974 and are Class B.