DENVER -- Mention you're from California these days and the grocery bagger here sneers. The dry cleaner mutters. A welcome smile may dissolve into a snarl.

"I think of them as a plague of locusts," said Sally Janover, a Denver designer. "They go where it's good feeding, bringing their garbage with them. They're rude, self-centered, snobby and only interested in their own well-being."

Once welcomed as a cure-all for Colorado's wheezing economy, migrating Californians nowadays are widely viewed as an invading horde. Many "natives" -- as anyone in Colorado long enough to get a haircut declares himself -- believe Californians are polluting the Rocky Mountain way of life with big money and ambitions and lack of respect for the state's natural beauty.

"They are the harbingers of the future," said former governor Richard Lamm. "They have compromised their quality of life, and they are looking for other places to go. If you want to see Denver tomorrow, go to Los Angeles today."

The influx has been happening elsewhere in the West since the 1980s -- with tens of thousands of Californians streaming into Washington, Oregon, Nevada and Arizona. About 160,000 have abandoned the Golden State in the last five years for Colorado -- a significant addition to a state population of 3.6 million.

This, in turn, is helping feed an economic phenomenon that is changing the character of the state and the people who live here. New professionals have boosted housing prices while fueling an expansion in ancillary businesses like dry-cleaners and groceries. Demand for everything is up, creating jobs, but also creating longer waits that hurt the quality of life.

Enclaves like Castle Rock and Highlands Ranch, both south of Denver, have become magnets for California castaways because of inexpensive land and beautiful scenery. Golden, rolling hills are now spotted with $100,000-plus homes and the bagel shops and coffee houses that followed.

Katherine Young, a television and film producer who fled the Los Angeles area in 1989, wised up after a hostile stranger administered a California yuppie test during one of her first visits to a Colorado Safeway.

"This guy put his hands on his hips and said, 'I'll prove that you're a California yuppie. Do you have a coffee bean grinder?' I said yes, and he said, 'See.' " Now, she says, "I'm smart enough not to trumpet the fact that I'm from California."

Bashing out-of-staters is hardly new. Colorado's booms and busts date back to the Cripple Creek gold rush of the 1890s, with corresponding influxes of dream seekers. Before Californians there were Texans, drawn to the late-1970s energy boom under President Jimmy Carter's shale oil program. That spawned bumper stickers with the warning: "Don't Californicate Colorado," or one with a simple declaration, "Native." The animosity died down in the 1980s, when a severe recession gave Coloradans other things to complain about.

But the dominance of the old mining and agricultural industries is giving way to a new economic boom fueled by high-tech industry and tourism that has put the growth issue front and center.

Everyone wants to be the last person to move in. "A group of amenity-driven Californians are coming here ... changing housing prices, filling the coffee shops ... but it's not the decline of Western Civilization," said Patricia Nelson Limerick, a history professor at the University of Colorado, Boulder.

Whatever the price to a way of life, Californians are doing their part to fuel the Colorado economic boom.

The Denver Chamber of Commerce estimates that roughly half of the new businesses expanding or relocating into the state are from California. Denver's median housing price rose 10 percent last year while Los Angeles and San Francisco stayed about the same, according to the National Association of Realtors. A new baseball park is in the works. Nordstrom Inc. is planning its first store. There's even talk of a mini-film industry starting in the state.

John Ramstetter, general sales manager for a Lexus dealership south of Denver, said Californians are nearly 10 percent of his business -- trading in cars like Jaguars, Audis and Mercedes, what one anti-Californian called "land-arks."

But there is a downside to all the growth. Although the state still has plenty of wilderness, there's concern that the beautiful mountains will soon be dotted by condominiums or tract homes. In the Denver metropolitan area, schools and highways are becoming more crowded and pollution remains a sore spot.

The bottom line is a concern over how many people can fit into the state's 104,000 square miles -- nearly equal to Pennsylvania, Virginia and West Virginia combined -- without destroying its character. More than 80 percent of Colorado's population is clustered along a 150-mile long strip on the eastern edge of the Rockies known as the Front Range. "Coloradans have the idea that we'd just as soon not have this many people here," said Jim Westkott, the state demographer. "They hike out to their favorite spot and there are 25 people there, when it used to be empty."

Colorado is in the fifth year of a wave of California emigrants seeking respite from the calamities of the West Coast, where earthquakes, mudslides, drought, fires, racial tensions and the high cost of living have eaten at the American Dream.

"When people have screwed up their own areas, then they come here," said Lamm, director of the Center for Public Policy and Contemporary Issues at the University of Denver and a former Californian. He estimates that in the last four years 400,000 Californians have fled.

"We came here because we didn't want our kids to grow up in California," said Young, 36, the former Los Angeles producer and mother of three. "It's extremely crowded, extremely expensive. You don't have control of your child's schooling."

Young and her husband, Dan, sold their 1,200-square-foot condo north of Los Angeles for $148,000 in 1989 and bought a $90,000 house in Castle Rock that was more than twice as big. Their car insurance dropped dramatically, as did the length of their commutes.

Many newcomers are like Young, flush with money for down payments after cashing out of the California real estate market and searching for a better way of life. Their house south of Denver has a spectacular view of the Rocky Mountains and is a two-hour drive to skiers' nirvana.

"There's a whole lot of West Coasters in Colorado, and the people I've met overall are happy," Young said. "We're huddled together like a bunch of refugees. You can still find the American Dream here."

But throwing around so much cash also has had an impact on the Coloradans who were trying to make it up the economic ladder.

Michelle Davis, who works at a beauty salon in Denver's upscale Cherry Creek section, still is smarting from the Californians who bought a house she had her heart set on in the western suburb of Lakewood.

"They had cash they plopped down and stole the house from under me," said Davis.

Colorado's population of 3.6 million is projected to increase to 4.7 million by 2020, according to the Colorado Division of Local Government. One estimate said it could double in 20 years. In response, Gov. Roy Romer (D) has proposed sweeping changes that will help localities get a handle on growth and help plan their communities.

Don Brookins isn't from California or Colorado, but the cameraman for a local television station thinks he knows why people come. They've heard about the 300-plus sunny days per year, cool summer evenings, natural beauty and a low cost of living. Then his voice softens to a whisper to conclude with a cautionary note: "You'll love it here ... but don't tell anybody."