Do you have a Loopnet account? I did a quick search on Loopnet for Fullerton using 400-1000 sf/offic space and quickly found 33 properties. When you expand to the surrouding area, 100 properties come up showing availability bet. 400-1000 sf.
As far as the rent goes, 0.75/sf/mo - 2.50/sf/mo is a pretty big spread. In my market, we quote rates as price/sf/year, and if you convert the numbers it translates as $9/sf/yr - $30/sf/yr, which I think illustrates the spread better.
Also, I'm in Philly so I can't really tell you what a good rate is, you'll need someone local. Also, the rate will be higher or lower based on the location, the size of the space, the quality of building (class A, B, C), quality of tenants, occupancy rate, how the space will be delivered (turn key, vanilla shell, etc.), and the type of lease (net, gross, etc.).
Good luck...