Compared to the rest of the San Diego market, the El Cajon region has smaller rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 15 listings have been posted online, 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 on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,500 sqft. Most properties in this market are approximately 2 stories. Most buildings in this market were built in 1977 and are Class B.