The USA Water Polo National Aquatic Center, where the men's and women's US Olympic water polo teams train, is located on the US Military Joint Forces Training Base in Los Alamitos. The facility is also used for major water polo tournaments, swim classes and local swim teams. The Joint Forces Training Base includes the Los Alamitos Army Airfield.
As of the census of 2000, there were 11,536 people, 4,246 households, and 3,035 families residing in the city. The population density was 1,110.7/km² (2,875.5/mi²). There were 4,329 housing units at an average density of 416.8/km² (1,079.1/mi²). The racial makeup of the city was 76.97% White, 3.20% African American, 0.58% Native American, 9.49% Asian, 0.33% Pacific Islander, 5.37% from other races, and 4.07% from two or more races. Hispanic or Latino of any race were 16.02% of the population.
There were 4,246 households out of which 36.6% had children under the age of 18 living with them, 48.4% were married couples living together, 17.1% had a female householder with no husband present, and 28.5% were non-families. 21.8% of all households were made up of individuals and 7.7% had someone living alone who was 65 years of age or older. The average household size was 2.62 and the average family size was 3.06.
In the city the population was spread out with 25.2% under the age of 18, 7.8% from 18 to 24, 30.8% from 25 to 44, 21.3% from 45 to 64, and 14.8% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 90.0 males. For every 100 females age 18 and over, there were 84.4 males.
The median income for a household in the city was $55,286, and the median income for a family was $60,767. Males had a median income of $49,946 versus $36,002 for females. The per capita income for the city was $26,014. About 4.1% of families and 5.2% of the population were below the poverty line, including 4.9% of those under age 18 and 8.8% of those age 65 or over. Property prices in the city have increased dramatically over the past 20 years.