The State Equalized Value (half of the assessed or market value) shown in the Public Records is $155,420 for 2008 down from $168,720 in 2007. This value could be somewhat high as we are in a declining market. It appears that the property sold for $650,000 in 2005, although it was listed as a different address. Other vacant lots about the same size have sold in 2006 for $325,000 and 2007 for $495,000. For more information on comparable sales, please feel to contact me.
I think you would need a buyer's agent to give you an estimation of a good price. Someone needs to look at the property with you and evaluate it against other similar properties.
If you do not have a buyers agent and you would like help with this, please feel free to let me know.