You didn't say where or how you are stuck so I made some assumptions.
Have you ordered copies of the obits? Obituaries are great sources of information. There is an obituary volunteer at freepages.genealogy.rootsweb.ancestry.com/~obitl/volca.html
Scroll down to San Diego Co.
If he can't find them, contact the San Diego Library, sdcl.org
Hover over Community Services
Click on Libraries
Click on AskALibrarian on right-hand side of screen
Here's information that I found.
Born: 28 Nov 1873, San Diego County, CA
Residence: September 12, 1918 St. Joseph's Sanitarium, San Diego
Occupation: cement worker @ St.Joseph's Sanitarium, San Diego
Nearest Relative: Maria Seria Monteil, St. Joseph's Sanitarium
Source: u. S. World War I Draft Registration Cards 1917-18.
In 1920 the family was living in El Cajon, San Diego, CA.
Eleut* Montiel, b. CA, 48, laborer street.
Mary, wife, b. mexico, 37.
Mary, b. CA, 12.
Anita, b. CA, 11.
William, b. CA, 8.
Alexander J., b. CA, 6.
A maria C. Montier
Married April 1922
Carlos B. Morales
Residence: El Cajon, San Diego Co.
Source: RootsWeb Marriages, userdb.rootsweb.ancestry.com/marriage...
In 1940 Alexander and family were living in San Diego, San Diego.
he's shown on the Census as Alexander Montillo, b. CA, 27, education=8th grade, picker lemon packing plant.
Laureta, wife, b. Mexico, 27, education=3rd grade.
mary Esher, b. CA, 5.
Rosa, b. CA, 3.
Edward, b. CA, 1.
It looks like Mary Esther Montiel b. June 4, 1935 San Diego, San Diego married a Tony Lopez.
Source: Forsberg Family Tree, trees.ancestry.com/tree/1608742/person/6003914575. However, you need to verify this before entering into your database.
Mary E. lopez
Born: 4 June 1935
MAYBE Last Residence: San Diego, San Diego
Died: 3 oct 1999
Her soc. sec. # was assigned in CA in 1952.
Source: Social Security Death Index.
You can verify that this is your Mary Montiel but ordering a copy of her obituary (if one was published).
In 1930 Mary and sons were living in El Cajon.
Mary Cesena, 48.
William Montiel, 18.
Alexander Montiel, 16.