MONTERREY, Mexico - It took 7-Eleven Mexico SA a dozen years to open its first 100 stores in northern cities like Monterrey. It took just a year to open the last hundred. Cramped mom-and-pop minimarts are giving way to brightly lighted 24-7 convenience stores preferred by a new generation that embraces a more American lifestyle - and the businesses that have long been a part of it. The joint venture between Grupo Chapa of Monterrey and Dallas-based 7-Eleven Inc. isn't just growing rapidly in the Americanized north. It's also a hit in the Mexican capital, bringing Cafe Select and Big Bite hot dogs to one of the world's most populous - and hungriest - metro areas. "The coffee is really good, the store is well stocked, and it's open 24 hours a day," said Guillermo Sanchez, 19, a cook who buys breakfast at a Mexico City 7-Eleven near his workplace. Luis A. Chapa, chairman and chief executive of 7-Eleven Mexico, said Mexicans have quickly become used to a higher level of service. "That is the new standard, the new benchmark: cleanliness, freshness, hygiene, good lighting, security, quality products," he said. Ever since the North American Free Trade Agreement took effect in 1994, an open question has loomed over Mexico: Would Mexicans embrace American retailers on a mass scale? In the case of 7-Eleven, the answer is clear. Sí. Definitivamente. "Big companies see in these emerging markets an opportunity to serve a market that is relatively underdeveloped in its standards," Chapa said. "They see an economy with more than 100 million people. They see a growing economy. They see an economy with great possibilities of increasing per-capita income. They see an economy of young people where lifestyles are becoming more like those in other big cities in other nations." As a privately held company, 7-Eleven Mexico doesn't give out official sales figures, but Chapa said they are upward of $350 million annually. One of the company's strengths, he added, is offering products the competition can't: ready-to-eat Big Lunch sandwiches and Big Donuts, specially formulated Cafe Select coffee and, of course, Slurpees. Chapa expects by year's end to have 600 stores for the joint venture, which was started in 1976 with just four units. Back then, it wasn't called 7-Eleven, but Super Siete, to give it a Mexican flavor. Occasionally, there are tensions over the foreign influences. Artists and cultural activists in the southern state of Oaxaca successfully protested to keep McDonald's out of the capital city's central plaza. Similar groups have opposed a Costco in Cuernavaca, south of Mexico City, and a Wal-Mart-owned supermarket near the Teotihuacan pyramids north of the capital. Both have since opened. Far more challenging, however, is the Mexican competition. The convenience store chain OXXO has 3,466 stores in 90 cities across the nation. OXXO says it has 50 percent of the market and was founded just one year after Super Siete. The chain also proudly states on its Web page that it is a "100 percent Mexican company." In concept and pricing, it is similar to 7-Eleven. OXXO is owned by FEMSA, the largest beverage company in Latin America, with Coca-Cola bottlers and one of Mexico's two major beer companies. Jose Alberto Galvan, a financial analyst at BBVA Securities in Mexico City, said that despite the rapid growth of convenience stores in Mexico, there appears to be plenty of market for everyone. "I think there is still a lot of potential for growth ... as per-capita income rises and Mexico's demographics change toward consumers who are accepting of these types of stores."