Houston offers advertisers a large population and a huge and growing Hispanic market.
The following information is excerpted from the Wikipedia article on "The Demographics of Houston":
As of the census of 2000, there were 1,953,631 people, 717,945 households, and 457,330 families residing in the city. The population density was 3,371.7 people per square mile (1,301.8/km²). There were 782,009 housing units at an average density of 1,349.6 per square mile (521.1/km²). If the city of Houston were a U.S. state, it would rank 36th in population—its 2.01 million residents in 2004 would place it behind Nevada and ahead of New Mexico. In 2005, the Greater Houston area had a population over 5.7 million.
There were 717,945 households out of which 33.1% had children under the age of 18 living with them, 43.2% were married couples living together, 15.3% had a female householder with no husband present, and 36.3% were non-families. Twenty-nine percent of all households were made up of individuals and 6.2% had someone living alone who was 65 years of age or older. The average household size was 2.67 and the average family size was 3.39. The median house price was $115,961 in 2009.
In the city, the population was spread out with 27.5% under the age of 18, 11.2% from 18 to 24, 33.8% from 25 to 44, 19.1% from 45 to 64, and 8.4% who were 65 years of age or older. The median age was 31 years. For every 100 females there were 99.7 males. For every 100 females age 18 and over, there were 97.8 males.
The median income for a household in the city was $36,616, and the median income for a family was $40,443. Males had a median income of $32,084 versus $27,371 for females. The per capita income for the city was $20,101. Nineteen percent of the population and 16% of families were below the poverty line. Out of the total population, 26.1% of those under the age of 18 and 14.3% of those 65 and older were living below the poverty line.Wikipedia
As of 2011, the city is 44% Hispanic. As of 2011, of the city's U.S. citizens that are Hispanic, half are at voting age or older.