The typical asking rate per listing is in the $30's per square foot per year. The Vista region is going through a a rise in rates. In the last 3 months, the median rate rose $33 per sqft per year.
Compared to the rest of the San Diego market, the Vista region has lower rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 41 listings have been listed, so you'll want to check back regularly for new listings. About 56% of the available space in the Vista 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 1,550 sqft. Most properties in this region are approximately 2 stories. Most buildings in this region were built in 1999 and are Class B.