According to the United States Census Bureau, the CDP has a total area of 2.9 square miles (7.4 km²), all of it land.
As of the census of 2000, there were 4,575 people, 1,391 households, and 1,065 families residing in the CDP. The population density was 1,591.9 people per square mile (615.5/km²). There were 1,471 housing units at an average density of 511.9/sq mi (197.9/km²). The racial makeup of the CDP was 61.99% White, 0.59% African American, 1.99% Native American, 3.26% Asian, 0.26% Pacific Islander, 27.63% from other races, and 4.28% from two or more races. Hispanic or Latino of any race were 41.14% of the population.
There were 1,391 households out of which 43.4% had children under the age of 18 living with them, 55.1% were married couples living together, 16.0% had a female householder with no husband present, and 23.4% were non-families. 18.8% of all households were made up of individuals and 8.3% had someone living alone who was 65 years of age or older. The average household size was 3.29 and the average family size was 3.75.
In the CDP the population was spread out with 35.1% under the age of 18, 8.7% from 18 to 24, 29.4% from 25 to 44, 17.8% from 45 to 64, and 9.1% who were 65 years of age or older. The median age was 30 years. For every 100 females there were 97.7 males. For every 100 females age 18 and over, there were 94.8 males.
The median income for a household in the CDP was $31,734, and the median income for a family was $34,444. Males had a median income of $29,787 versus $20,625 for females. The per capita income for the CDP was $11,865. About 19.5% of families and 21.0% of the population were below the poverty line, including 25.0% of those under age 18 and 17.5% of those age 65 or over.
In the state legislature Keyes is located in the 12th Senate District, represented by Republican Jeff Denham, and in the 26th Assembly District, represented by Republican Greg Aghazarian. Federally, Keyes is located in California's 19th congressional district, which has a Cook PVI of R +10 and is represented by Republican George Radanovich.