Natividad Gallegos, who lives in a poor section of Acapulco, said she returned from shopping Monday to find house buried by a landslide from a neighboring hill.
"When I got home I saw a lot of strangers with picks and shovels, digging where my house used to be," she said, weeping.
She said she lost six members of her family in the landslide, including her two children.
The coastal town of Coyuca de Benitez and beach resorts further west of Acapulco — including Ixtapa and Zihuatenejo — were cut off after a river washed out a bridge on the main coastal highway.
Marcela Higuera, who runs a bread stall in the Coyuca market, said the only aid that had arrived so far was a helicopter that rescued stranded flood victims.
"Flour's already run out. There isn't any in Coyuca," she said. "This is the worst storm that I've seen."
"There are hundreds of people in shelters and they're begging for clothes and blankets because everything they have is wet. They had to leave without taking anything."
She said the Coyuca River had not only swept away the bridge, but also riverside restaurants, and had flooded low-lying neighborhoods.
Remnants of Manuel continued to drench Mexico further up the Pacific coast and the U.S. National Hurricane Center said there was a chance it could regain force near resorts at the tip of the Baja California Peninsula.
Mexico's Gulf Coast states meanwhile were trying to recover from Hurricane Ingrid, which drove tens of thousands of people from their homes and blocked highways. That storm was dissipating over northeastern Mexico on Tuesday.
The Mexican government said the country had not seen a similar weather crisis since 1958, when it was simultaneously hit by two tropical storms, also on separate coasts.
The governor of the Gulf Coast state of Veracruz announced that 12 people died when a landslide smashed into a bus traveling through the town of Altotonga, about 40 miles (65 kilometers) northwest of the state capital.
More than 23,000 people fled their homes in the state due to heavy rains spawned by Ingrid, and 9,000 went to emergency shelters. At least 20 highways and 12 bridges had been damaged, the state's civil protection authority said.
Mark Stevenson and E. Eduardo Castillo contributed from Mexico City.