According to the United States Census Bureau, the CDP has a total area of 1.5 square miles (3.9 km²), all of it land.
Heber was founded in 1903 by the California Development Company. The first post office at Heber opened in 1904, having been transferred from Bradtmoore. The name honors A.H. Heber, president of the California Development Company.
As of the census of 2000, there were 2,988 people, 729 households, and 677 families residing in the CDP. The population density was 2,003.9 people per square mile (774.3/km²). There were 756 housing units at an average density of 507.0/sq mi (195.9/km²). The racial makeup of the CDP was 34.34% White, 0.64% Black or African American, 0.60% Native American, 0.27% Asian, 61.85% from other races, and 2.31% from two or more races. 97.52% of the population were Hispanic or Latino of any race.
There were 729 households out of which 53.4% had children under the age of 18 living with them, 66.1% were married couples living together, 19.9% had a female householder with no husband present, and 7.0% were non-families. 5.9% of all households were made up of individuals and 4.0% had someone living alone who was 65 years of age or older. The average household size was 4.10 and the average family size was 4.24.
In the CDP the population was spread out with 34.8% under the age of 18, 9.5% from 18 to 24, 29.4% from 25 to 44, 17.3% from 45 to 64, and 8.9% who were 65 years of age or older. The median age was 29 years. For every 100 females there were 91.3 males. For every 100 females age 18 and over, there were 87.0 males.
The median income for a household in the CDP was $28,221, and the median income for a family was $29,526. Males had a median income of $23,056 versus $19,231 for females. The per capita income for the CDP was $8,847. About 21.6% of families and 22.9% of the population were below the poverty line, including 28.9% of those under age 18 and 18.1% of those age 65 or over.
In the state legislature Heber is located in the 40th Senate District, represented by Democrat Denise Moreno Ducheny, and in the 80th Assembly District, represented by Republican Bonnie Garcia. Federally, Heber is located in California's 51st congressional district, which has a Cook PVI of D +7 and is represented by Democrat Bob Filner.