The Hall family was driving back to California on the foggy coastal highway when a car flashing red lights and blaring its siren pulled up behind them. A police shakedown, thought Debra Hall as her husband, Christopher, veered to the side of the dark road.

Having made many trips to Baja California, they knew a payoff was just part of the price of a visit. This time, returning from the Baja 1000 off-road race, they figured $40 would suffice and they'd be back at their El Cajon home within an hour.

Instead, several heavily armed, masked men surrounded their truck and trailer and pointed guns at their heads, the start of an hours-long assault that ended with Debra, Christopher and their two children running for their lives through the hills.

The Hall family's ordeal last week was the latest in a string of assaults against Americans that has shocked longtime visitors and severely undercut a recent anti-crime initiative aimed at polishing Baja California's image as a tourist-friendly destination. In a region where most visitors expect the occasional extortion attempt by police, the recent crime wave has seen attacks become more aggressive, often carried out by heavily armed men operating with paramilitary-style precision.

Surfers have been assaulted at gunpoint on beaches and at campgrounds. One woman was sexually assaulted. Expensive trucks, trailers and boats have been carjacked.

At least seven assaults in the past few months have been reported in the media or on websites of Baja surfing and fishing groups. The State Department, which has a consulate in Tijuana where citizens can report crimes, said a long-standing travel alert remains in effect for border regions.

It's not clear whether the incidents are isolated or represent a trend, said Michele Bond, the department's deputy assistant secretary for Overseas Citizens Services.

But the crime wave is enough to frighten some longtime visitors, including surf club owners who have canceled operations and some prominent off-road racers who may not compete in future Baja events.

Most of the assaults have occurred at night in the coastal area between Tijuana and San Quintin, a 190-mile stretch dotted with surf beaches, campgrounds, resorts and golf courses.

Surf school owner Pat Weber, of Encinitas, and his girlfriend, Lori Hoffman, were assaulted in October in their recreational vehicle within sight of 30 other campsites on a beach south of Ensenada.

Two masked assailants shot up the vehicle when Weber initially refused to open the door. For the next 45 minutes, the men terrorized the couple, who had gone to Mexico after evacuating their home during the wildfires.

Hoffman said she was sexually assaulted in front of her boyfriend. Then the men made off with $8,000 worth of laptops, jewelry, tools and other items. One of the men disappeared into the night with Weber's acoustic guitar slung over his shoulder.

"These guys were not novices," said Hoffman, who noted the attackers' creased pants, combat boots and sharpshooting skills. The incident was reported to Ensenada police.

Many experts say the timing of the crime wave is curious, coming just ahead of a change in administrations in Tijuana. Critics say former Mayor Jorge Hank Rhon bloated the police payroll with unqualified and corrupt cops.

With rumors flying that the new mayor, Jorge Ramos, whose term begins today, will fire hundreds of police, some rogue cops may be going on a last-minute crime spree, say some observers.

Ramos said one of his first acts as mayor will be to create a special tourist police force -- with different uniforms and cars than municipal police -- that will patrol the coastal highway, in effect, policing the police.

"Whatever it takes, it'll be done," said Oscar Escobedo Carignan, Baja's new secretary of tourism. Escobedo said the state remains a safe travel destination. "I don't want to downplay what happened. We take it seriously. And we're making every effort to control it."

But promises of a crackdown won't convince the Halls to return to Mexico.

Christopher and Debra, along with their 16-year-old son and 21-year-old daughter, were returning home from Los Cabos about 1 a.m. after participating in the Baja 1000. The family had driven the length of the peninsula many times, so when the siren blared behind them as they entered Tijuana, they thought nothing of it.