After lashing Mexico's Cancun region with 135-mph winds, Hurricane Wilma turned to the northeast, intensified into a dangerous Category 3 storm and was barreling toward Florida, where residents took shelter after days of nervous anticipation and emergency preparedness leaders made last-minute pleas to those who resisted mandatory evacuation orders.

Many residents fled the Florida Keys and the coastal areas of Naples and Fort Myers, where evacuations were ordered. Up and down the roadways of southwestern Florida, shopping centers and fast-food restaurants were boarded up, and many neighborhoods seemed nearly deserted.

But thousands of residents stayed in their homes and ignored mandatory evacuation orders, particularly in Key West, where some people disregarded repeated calls to leave, state and local officials said, even though the storm surge was forecast to be five to eight feet above normal tide there and as high as nine to 17 feet where Wilma makes landfall.

"I cannot emphasize enough to the folks that live in the Florida Keys: A hurricane is coming," Gov. Jeb Bush said. "Perhaps people are saying, 'I'm going to hunker down.' They shouldn't do that. They should evacuate, and there's very little time left to do so."

He said 2,400 National Guard troops were mobilized to respond to Hurricane Wilma, and that medical personnel and provisions were ready to be trucked in.

R. David Paulison, the acting director of FEMA, said supplies had been massed in Jacksonville and at Homestead Air Force base in south Miami-Dade County, near the Keys' Monroe County. Paulison said the agency had about a thousand people in Florida, many of them already there because of the earlier hurricanes.

An estimated 15,000 people were in shelters, Red Cross officials said. About 160,000 had been ordered to evacuate in anticipation of Wilma's arrival ashore at dawn Monday.

During Wilma's two-day battering of Mexico, the winds shattered windows, peeled roofs off and propelled the Caribbean Sea into hotel lobbies. On Sunday, looters overran some Cancun stores.

At least three people were killed in Mexico, following the deaths of 13 in Jamaica and Haiti. On Sunday, Wilma's winds hit western Cuba while the eastern side was buffeted by Tropical Storm Alpha as it weakened to a tropical depression forecast to dissipate in a few days in the open Atlantic.

At 1 a.m. Eastern time, Hurricane Wilma was roaring toward southwest Florida at 18 mph with winds that had strengthened to 115 mph, the National Hurricane Center said.

Wilma was expected to swiftly cross narrow Florida, spin off tornadoes, rain as much as eight inches and batter Atlantic Coast cities with hurricane-strength winds Monday, forecasters said.

Floridians anticipating Wilma's arrival were of two minds about the approaching danger: While some chose to remove themselves from the hurricane's projected path, others chose to stay, in many cases defying ominous warnings from emergency workers who toured some neighborhoods with bullhorns.

The scenes of destruction from Mexico, following the devastation of Hurricanes Katrina and Rita, have made many people more aware of the dangers of the storms, some officials said.

"I've been here for 22 years," said Naples Police Chief Steve Moore, "and this is the best-prepared this city has ever been."

He estimated that about 75 percent of residents in the city's coastal areas had left.

"They see this as a storm that is coming right at them," he said. "People now are more aware. They've seen the devastation in Mississippi and Louisiana, and they don't want any part of it."

Still, about one-fourth of the residents of Naples chose to stay, he estimated, and in Key West, local officials said that about 80 percent of residents are holding out.

There, an almost carnival-like atmosphere prevailed in some small gatherings in the city's downtown, where people boasted of having ridden out other storms.

"Another Day, Another Hurricane!" read the message spray-painted across the plywood protecting Fast Buck Freddie's, a department store on Duval Street, the city's main drag.

All along Duval, people could be seen biking and walking their dogs. A few bars were open and were crowded, well past sunset.

Estamarie Stover and her husband, Sandy, were walking up Duval Street on Sunday afternoon. "We had hotel reservations in Miami," she said, but did not expect to use them.

"We decided if it was a 3 or worse and it was coming right at us, we would leave," he said before the hurricane center announced that very reality.

Key West High School would serve as a shelter of last resort, but it would have no amenities, city spokesman Michael Haskins said.

Key West Mayor Morgan McPherson said those staying in the city are "taking a big gamble."

Police were sent to the city's trailer parks and low-lying areas to reiterate the warning to leave.

"All you can do is keep suggesting," McPherson said in an interview.

Most longtime Floridians have grown accustomed to the hurricane threat and have adopted their own ways of evaluating when to evacuate. Their calculations depend on forecast wind speed and storm surge but are only loosely related to the warnings of emergency officials.

Bonnie Campbell, a hotelier who was walking her French poodle near the beach on Naples Sunday afternoon, said she had made a hotel reservation in Orlando in case Wilma had been forecast a Category 3 or higher. But for a Category 2, she said Sunday afternoon before the storm strengthened, she was merely leaving her home, which is in an evacuation area, and staying in her Naples hotel just outside the evacuation zone.

"I think people are overreacting -- or maybe not -- because of what happened in Louisiana," she said.

She said three of her neighbors are staying despite the evacuation order. "Their homes are 12 feet above sea level," she said. Some estimates for the storm surge in Naples have come in below that. "For them, it's a calculated risk."

Elsewhere, residents said they felt a healthy fear of Hurricane Wilma.

In Everglades City on the southwest coast, a low-lying city of mobile homes and homes on stilts, Mayor Sammy Hamilton Jr. said they were expecting severe flooding because even with light winds and rain, water backs up in the streets. He said after Hurricane Donna in 1960, the city was under 12 feet of water.

"It'll kill us," he said. "It'll come on us like a tidal wave."

At midday Sunday, the area appeared almost deserted. The mobile home parks were empty, or nearly so. The airboat concessions were closed. But a kind of giddy hurricane humor prevailed.

"Fred Loves Wilma," a sign outside a store in Everglades City read. "We don't."

Cauvin reported from Key West.

Charlene Long, background left, and her daughter Christina Long greet Vivica St. Surin, 3, while waiting for Hurricane Wilma in a shelter near Naples. The hotel zone of Cancun, Mexico, is battered by Hurricane Wilma after winds and torrential rains hit the resort town. People stroll on the beach in Naples, Florida as Hurricane Wilma churns over Cancun, Mexico. Wilma is expected to hit Florida's southwest coast today.