Compared to the rest of the San Diego market, the Spring Valley region has greater rates, and you'll have to negotiate above asking rent to be in this hot region.
In the last 90 days, 3 listings have been made available, which means listings 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 posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,190 sqft.