The typical asking rate per listing is in the $10's per square foot per year. The El Cajon submarket is seeing a decline in rates. In the last 3 months, the median rate fell $4 per sqft per year. That's a 19% decline in rent.
Compared to the rest of the San Diego market, the El Cajon submarket has less expensive rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 16 listings have come on the market, which means listings are probably going fast. 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.
The standard measurement for office space in this area is around 710 sqft. Most properties in this area are close to 2 floors. Most buildings in this market were built in 1977 and are Class B.