The victims were "psychologically affected" by the attack and received treatment, the mayor said.
Spain's Foreign Ministry had already issued a travelers advisory on its website for Acapulco before the Monday attack, listing the resort as one of Mexico's "risk zone," though not the worst.
"In Acapulco, organized crime gangs have carried out violence, though up to now that has not affected tourists or the areas they visit," the advisory states. "At any rate, heightened caution is advised."
The attack came just three days after a pair of Mexican tourists returning from a beach east of Acapulco were shot at and slightly wounded by members of a masked rural self-defense squad that has set up roadblocks in areas north of Acapulco, to defend their communities against drug gang violence.
The vigilantes say the Mexican tourists failed to stop at their improvised roadblock.
Walton said the city was already contemplating ways to revive the city's image.
"We have to look at an advertising campaign to say that not everything in Acapulco is like that," Walton said. "This happens everywhere in the world, not just in Acapulco or in Mexico."
The attack was particularly embarrassing for Mexico, because it came just four days after Tourism Secretary Claudia Ruiz Massieu visited the International Tourism Fair held in Madrid to launch a "promotional offensive" depicting Mexico as a safe and attractive destination.
"This is Mexico's moment," Massieu said, describing it as "a safe country."
The granddaddy of Mexican resorts, Acapulco was glorified in Frank Sinatra songs and Elvis movies. Elizabeth Taylor was married there, John F. and Jackie Kennedy came on their honeymoon, and Howard Hughes spent his later years hiding out in a suite at the Princess Hotel, a pyramid-shaped icon in the exclusive Punta Diamante, or Diamond Point, zone.
Beheadings and drug gang shootouts, some on the city's main seaside boulevard, became more frequent after 2006, as gangs fought for control of the city's drug and extortion business.
Associated Press writer Bertha Ramos reported from Acapulco, and Mark Stevenson reported from Mexico City.