North – Nava Boulevard
South – Andres Bonifacio Street
East – Emilio Aguinaldo Street
West – Jose Rizal Street
This Barangay is also surrounded by other Barangays like Brgy. Tabing Dagat on the East, Brgy. Rizal on the South, Brgy. Pipisik on the West, and on the North we are facing the Historical Lamon Bay.
The land area of this Barangay is 4.400 hectares. It has a population of about 1500 residents with 190 household and 300 families.
For tourists, we have the Citadel or Castillo as a beautiful spot to visit. This has been used by soldados and often raided and robbed by Pirates during the olden times. It is said to have a tunnel leading under the 417 years old church which is also another Tourist Spot being the oldest and mother church to the neighboring towns. This church compound occupies a block in the heart of the Barangay.
The Barangay started to be Purok Castillo, the chairman of which was Gil Nosas. When this was transformed to Barangay like other barangays in the town of Gumaca, this was named Barangay San Diego in honor of the Patron Saint of the town. Poblacion has to be affixed to its name as there is a barrio named San Diego also. Gil Nosas was reappointed as the Barangay Chairman. In the 1979 elections, Gil Nosas had no opponent and continued his term. He was followed by Quirico Dionco, Elmer Hong, Macimo Guinto, Mateo Cabangon and Arnold F. Portugal; Teresita Macaraeg and Vermont Noscal. Thru the concerted effort of the people of the community, aid from the National Provincial and Local Government came pouring in, which gave the Barangay the much needed improvement like paving streets with gutters and canals, Barangay Hall, Barangay Health and Police Centers, Daycare Center, and the Sangguniang Kabataan Hall. The Sangguniang Kabataan headed by Chairman Michael Arguesa had also their Mini-Playground. This was equipped with playground Apparatus like seesaw, slide and Swing which children from all parts of the town enjoy, street lightning has also been very much improved thru the initiative of the Barangay Kagawads.
Most residents of this Barangay are private and government employees. Some are teachers, some are municipal employees. There some who are having their own businesses like stores, bakeries, pawnshop, etc. There are establishments situated in this barangay like the Holy Child Jesus College, St. Didacus Institute, the Computer School ASTI. We have also Banks like Allied Bank and the Coconut Planters Bank.
The people of this Barangay is well taken cared of by a Rural Health Unit. We are visited by the Rural Health Doctor, Nurse and Midwife regularly.