There are certainly good neighborhoods in Weston Ranch. There are also some bad ones as well. My personal opinion is that there are more bad than good. I would suggest other areas of Stockton before Weston Ranch. It is very important to know the neighborhoods and School Districts prior to purchasing a home. I highly recommend Lincoln Unified School District and Lodi Unified over others in the area.
Also, look at the sites below to learn about crime in a specific area.
http://webmaps.stocktongov.com/mapcentric/pub/spdmap.aspx Stockton PD
http://www.sjsheriff.org/activitylog.htm San Joaquin County Sheriff
Hope this helps a little. I am sure other agents will provide their opinions on Weston Ranch as well.
Let me know if I can be of anymore assistence.