Most listings are in the $30's per square foot per year. The El Cajon region is experiencing a a boost in rates. In the last 3 months, the median rate went up $13 per sqft per year. That's a 74% increase in rent.
Compared to the rest of the San Diego market, the El Cajon region 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 been posted online, which means new listings most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 100% of the office spaces in the El Cajon 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 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 1,430 sqft. Most buildings in this region are approximately 2 stories. Most buildings in this area were built in 1977 and are Class C.