Two major points:
A) A "Local Street" is defined under VC 40802 as:
a local street or road is one that is functionally classified as "local" on the "California Road System Maps," that are approved by the Federal Highway Administration and maintained by the Department of Transportation. When a street or road does not appear on the "California Road System Maps," it may be defined as a "local street or road" if it primarily provides access to abutting residential property and meets the following three conditions:
(A) Roadway width of not more than 40 feet.
(B) Not more than one-half of a mile of uninterrupted length. Interruptions shall include official traffic control signals as defined in Section 445.
(C) Not more than one traffic lane in each direction.
B) There is no such thing as everybody knows the limit is 45 simply because there is no law that sets the 45mph limit as a specific limit under specific circumstances. Alternatively, and with the description you gave, my gut feeling is that it would be a residential zone which in turn would be set at 25mph just as the officer had cited you for. To confirm whether it is a residential district, you would have to refer to VC...
VC 515. A "residence district" is that portion of a highway and the property contiguous thereto, other than a business district, (a) upon one side of which highway, within a distance of a quarter of a mile, the contiguous property fronting thereon is occupied by 13 or more separate dwelling houses or business structures, or (b) upon both sides of which highway, collectively, within a distance of a quarter of a mile, the contiguous property fronting thereon is occupied by 16 or more separate dwelling houses or business structures. A residence district may be longer than one-quarter of a mile if the above ratio of separate dwelling houses or business structures to the length of the highway exists.
So you'll have to look at a satellite image (Google Maps would suffice) of the street where your alleged violation occurred, then pinpoint the specific location of the violation (usually indicated on the citation), that point would then be the center point for your count. You would then mark the length of 1/4 mile (or 1320 feet) on the map. Meaning you would then have 1/8 of a mile on one side of the location of the violation and the other 1/8 being on the other side of the violation location. And then you would count residences/properties.
If it does turn out to be a "residence district", then your defense becomes extremely difficult
Of course, feel free to post the name of the street, the exact location of the violation, the name of the city, along with any additional info you would care to provide.
And the fact that the officer(s) could not write them fast enough is not going to affect the validity of your citation!