Avondale Homes for Sale and MLS Search. The city of Avondale is in Maricopa County and adjacent to Phoenix. It has a population of 76,238 and covers an area of 41.3 square miles. It was incorporated in 1946. Avondale is a sports mecca. Home to the Phoenix International Raceway it hosts two NASCAR races every year and is near many Cactus League stadiums.