According to the United States Census Bureau, it has a total area of 16.2 km² (6.2 mi²), 16.1 km² (6.2 mi²) of it is land and 0.16% is water. State Route 38 serves as its main street, called Mentone Boulevard as one enters Mentone from Redlands, then Mill Creek Road as one leaves the district and heads north toward Angelus Oaks and Big Bear.
39.5% of the households in Mentone had children under the age of 18, 49.9% were married couples living together, 13.6% had a female head of the household, and 31.4% were non-families. Of the 24.5% of households made up of individuals, 7.1% were 65 years of age or older. The average household size was 2.77 and the average family size was 3.33.
The population was spread out with 30.7% under the age of 18, 9.9% from 18 to 24, 30.8% from 25 to 44, 19.7% from 45 to 64, and 9.0% who were 65 years of age or older. The median age was 32 years. For every 100 females, there were 95.6 males. For every 100 females age 18 and over, there were 91.9 males.
The median income for a household was $41,225, and the median income for a family was $47,786. Males had a median income of $40,888 versus $29,495 for females. The per capita income for the CDP was $17,781. About 8.8% of families and 10.4% of the population were below the poverty line, including 11.7% of those under age 18 and 1.5% of those age 65 or over. Home of the Blackwell brothers.