On average, listings lease in the $20's per square foot per year. The National City region is experiencing a an increase in rates. In the last 3 months, the median rate went up $8 per sqft per year. That's a 50% increase in rent.
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 undervalued submarket.
In the last 90 days, 5 listings have been listed, which means leases most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
Even though the median size is 5,570 sqft, there are still 0 new listings below 2,000 sqft. Most buildings in this area are around 1 floors. Most buildings in this area were built in 1974 and are Class B.