Although some of them are certainly naturalized U.S. citizens returning to towns and villages of their birth after lifetimes of toil al otro lado, the director-general of FONATUR, the official agency for tourism development in Mexico, recently characterized the typical investors in that country's real estate as American "baby boomers who have paid off in good part their initial mortgage and are coming into inheritance money."

Indeed, according to the Wall Street Journal, "The land rush is occurring at the beginning of a demographic tidal wave. With more than 70 million American baby boomers expected to retire in the next two decades… some experts predict a vast migration to warmer -- and cheaper -- climates. Often such buyers purchase a property 10 to 15 years before retirement, use it as a vacation home, and then eventually move there for most of the year. Developers increasingly are taking advantage of the trend, building gated communities, condominiums, and golf courses."

The extraordinary rise in U.S. Sunbelt property values gives gringos immense economic leverage. Shrewd baby-boomers are not simply feathering nests for eventual retirement, but also increasingly speculating in Mexican resort property, sending up property values to the detriment of locals whose children are consequently driven into slums or forced to emigrate north, only increasing the "invasion" charges. As in Galway, Corsica, or, for that matter, Montana, the global second-home boom is making life in beautiful, natural settings unaffordable for their traditional residents.

Some expatriates are experimenting with exotic places such as the Riviera Maya in Yucatan or Tulum in Quintana Roo, but more prefer such well-established havens as San Miguel de Allende and Puerto Vallarta. Here the norteamericanos make themselves at home in more ways than one.

An English-language paper in Puerto Vallarta, for instance, recently applauded the imminent arrival of a new shopping mall that will include Hooters, Burger King, Subway, Chili's and Starbucks. Only Dunkin' Donuts (con salsa?), the paper complained, was still missing.

The gringo footprint is largest (and brings the most significant geopolitical consequences) in Baja California, the 1,000-mile long desert appendage to the gridlocked state-nation governed by Arnold Schwarzenegger. Indeed, Baja real-estate websites ooze almost as much hyperbole as those devoted to stalking the phantom menace of illegal immigrants -- just in a far more upbeat tone when it comes to the question of immigrant invasions.

In essence, Alta (Upper) California is beginning to overflow into Baja, an epochal process that, if unchecked, will produce intolerable social marginalization and ecological devastation in Mexico's last true frontier region. All the contradictions of post-industrial California -- runaway land inflation in the coastal zone, sprawling suburban development in interior valleys and deserts, freeway congestion and lack of mass transit, and the astronomical growth of motorized recreation -- dictate the invasion of the gorgeous "empty" peninsula to the south. To use a term from a bad but not irrelevant past, Baja is Anglo California's Lebensraum.

Indeed, the first two stages of informal annexation have already occurred. Under the banner of NAFTA, Southern California has exported hundreds of its sweatshops and toxic industries to the maquiladora zones of Tijuana and Mexicali. The Pacific Maritime Association, representing the West Coast's major shipping companies, has joined forces with Korean and Japanese corporations to explore the construction of a vast new container port at Punta Colonel, 150 miles south of Tijuana, which would undercut the power of longshore unionism in San Pedro and San Francisco.

Secondly, tens of thousands of gringo retirees and winter-residents are now clustered at both ends of the peninsula. Along the northwest coast from Tijuana to Ensenada, a recent advertisement for a real-estate conference at UCLA boasts that "there are presently over 57 real-estate developments… with over 11,000 homes/condos with an inventory value of over $3 billion… all of them geared for the U.S. market."

Meanwhile, at the tropical end of Baja, a gilded gringo enclave has emerged in the twenty-mile strip between Cabo San Lucas and San Jose de Cabo. Los Cabos is part of that global archipelago of real-estate hot spots where continuous double-digit increases in property values suck in speculative capital from all over the world. Ordinary gringos can participate in this glamorous Los Cabos real-estate casino through the purchase and resale of fractional time-shares in condominiums and beach homes.