On average, listings lease in the $20's per square foot per year. The La Mesa submarket is going through a an increase in rates. In the last 3 months, the median rate rose $24 per sqft per year.
Compared to the rest of the San Diego market, the La Mesa submarket has smaller rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 11 listings have been listed, which means spaces might be leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 109% of the available space in the La Mesa are subleases, so you might be able to find a shorter term or below market rent. 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 2,300 sqft. Most properties in this region are around 2 floors. Most buildings in this market were built in 1979 and are Class C.