No! Mexico’s population (mid-2010 estimate: 108,396,211) is not evenly distributed. Parts of central Mexico are very densely populated while there are relatively few people in the wide open spaces in northern Mexico. This is perhaps one of the most important features of Mexico’s human geography.
The Federal District and adjoining State of Mexico make up just over 1% of Mexico’s area, but house over 22% of the population for a density of 950 persons per km2. A central band, including Mexico City, encircled by Guadalajara, Aguascalientes, Xalapa, Veracruz, Puebla, Cuernavaca and Morelia covers only 10% of the land but contains over half of all Mexicans and has a density higher than that of northeastern USA (between Washington and Boston), UK, Germany or Italy.
The other 90% of Mexico has 50 million people, more than any other Latin American country except Brazil. Population densities in those areas are low.
In conclusion, some areas of Mexico are indeed crowded, but most of Mexico is not.
See this earlier post for a visually dramatic cartogram depicting Mexico’s population distribution.
Mexico’s population distribution and population density are analyzed in chapter 8 of Geo-Mexico: the geography and dynamics of modern Mexico.