The first copyright listed for Gary Soto's novel Buried Onions is 1996 and that is precisely the year in which the protagonist Eddie goes through his travails in the barrio of southeast Fresno. Soto reveals the exact year in chapter six when Eddie is in the Navy recruiting office. Eddie is wearing a Fresno State t-shirt with a picture of a bulldog, the university's athletic mascot. The recruiter comments on the the shirt, and tells Eddie that Jerry Tarkanian, the basketball team's second year coach, would turn them around. Tarkanian coached at Fresno State from 1995-2002 and they were indeed successful during his tenure. Tarkanian, a quite unique individual, is more famous for his time at the University of Nevada Las Vegas where he won an NCAA championship with the Runnin' Rebels in 1990. In the office there is also a picture of the president smiling from the wall, but Soto never indicates which president. Because it's 1996 the man would have been Bill Clinton. Throughout his novel Soto is quite accurate in his portrayal of Fresno in the 1990's, setting scenes at Fresno City College, Holmes Playground on First Street and Cuca's Restaurant which is still in business on F Street.  

What is the setting (including the place and time period) of Buried Onions?

"Buried Onions" takes place in Fresno, California.  The protagonist, Eddie, lives in a Mexican-American community.  Although I don't know an exact date for the plot, the time period is modern day. Enotes provides a more in depth setting analysis at the link below.