<p><em>"Property is in Villa Park (about a 1/2 acre, not microscopic for Orange County standards at least"</em> - So far, so good. Property lines are relatively easy to determine in Villa Park.</p>
<p><em>"Thinking of building a fence on a border with city property ("park" in name only)."</em> - This is the part where you may have gotten lucky. Many government organizations which hold public land in trust have their own rules that they must determine right of way, (property line for the city), when requested by an abutting land owner. Head on down to Villa Park civic center, don't call, to the civil engineering department. Villa Park probably does not have a survey department, but if it does, go instead to the survey department. And find out if Villa Park has a policy stating that they will determine their right of way. If they do, fill out the paperwork and wait, and wait, and ...</p>
<p><em>"Have been told the property line might lie up to 6 feet into the city property from where the current fence is"</em> - Do not believe anything you have been told unless it was told to you by a civil engineer or land surveyor who works in Villa Park. My own opinion is that most government organizations that hold public land in trust install fences about 6 inches into the city's right of way and build walls as close to right of way as is practicle.</p>
<p><em>"Do I go to the city or the county to find such records (as I am sure any paperwork the owner should have will be impossible to find) and what information will they give me?"</em> - Your deed has your property's legal description on it. Your deed legally determines what is your property. The legal description may reference a map. A copy of the map may be kept with the city and is most defintely kept by Orange County. But, there probably is no reason for you to access maps, because proceeding from a map is surveyor stuff. Figuring out your own property corners from a parcel map would be like me operating to remove your appendix while I was looking at an anatomy book.</p>
<p>To proceed further, I need to ask you another question. If there already exists a fence, why do you want to build another fence parallel to the existing fence?</p>