On average, listings lease in the $30's per square foot per year. The El Cajon submarket is going through a a rise in rates. In the last 3 months, the median rate rose $13 per sqft per year. That's a 74% increase in rent.
Compared to the rest of the San Diego market, the El Cajon submarket has smaller rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 16 listings have been posted online, which means office spaces most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. About 81% of the listings in the El Cajon 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 1,490 sqft. Most properties in this area are close to 2 floors. Most buildings in this market were built in 1978 and are Class C.