Prosecutors in Baja California state say the deaths happened late Saturday and early Sunday in various parts of the city, located across the border from San Diego, California.
Two of the dead were found shot to death in a home, two others in the trunk of a car, two in the street and one at a taco stand.
In the southern state of Guerrero, the bound bodies of two men were found near the capital, Chilpancingo, and a policeman was shot to death in the resort city of Acapulco.
Brutal slayings by drug cartels are on the rise. Officials estimate that more than 5,300 people have died in organized crime-related slayings this year.