A nondescript community surrounded by dry, scrubby hills at a 40-minute drive southeast of the Mexican capital, Milpa Alta doesn't look like the center of anything the world could be too interested in. But the ever-expanding rows of prickly pear cactus plants growing on virtually every square yard of the community's open space is out to change that. Like Salinas with its lettuce and Watsonville with its artichokes, Milpa Alta is the nopal capital of the world - a fact that is putting this town of 70,000 people on the world's vegetable and culinary maps. Nopal - pronounced ''no-pall'' or ''no-pall-ess'' in the plural - is the name from the indigenous Nahuatl language for the prickly pear cactus with its flat, oval leaves that adorns the Mexican flag. By extension, it is the name given the cactus's young, juicy leaves. Learn to say it, because the de-needled nopal leaf, which once graced the finest dishes of the Aztec emperors, is making its way from the fields and markets of Mexico to the supermarkets of the United States and beyond. Soon it's likely to turn up in your salad, as part of a casserole - or as a refreshing drink at your favorite Tex-Mex hangout. ''All you have to do is take off the needles, and it's ready,'' says Marcos Cruz Ramirez, a Milpa Alta nopal producer. ''You can slice it, eat it raw, cook it, roast it, squeeze it, puree it, or dry it. And whatever you do, it's tasty while high in vitamins and low in calories. That,'' he adds with a grin, ''makes nopal a food for today.'' Apparently Mr. Cruz's pitch isn't just the zealot's hype. From a few plants tried out in 1938 after other crops failed in the area's dry, rocky soil, Milpa Alta's nopal production has grown to surpass 150,000 tons a year. The area's nopal fields have doubled over the last decade to 20,000 acres. And with weekly exports to the US and Europe of 50 tons considered only the beginning, local growers are certain production will continue its surge. Why the nopal, and why now? From nopal producers to some of Mexico's finest chefs, all agree the nopal is a quintessential Mexican food and culinary ingredient that not only adds a tasty succulence to salads and hot dishes, but it is also right for an era of ''lite cuisine.'' ''My mother used to go out into the hills to gather the wild nopales, but now it's in the markets and even the supermarkets,'' says Maria Gutierrez, whose husband grows about 5 acres of nopal in Milpa Alta. Mrs. Gutierrez says she uses nopal three to four times a week in her cooking. ''It's a nice, tasty green for many dishes, and it makes a nice pie or marmalade,'' she says. Her favorite use of the cactus leaf, nopalitos (small nopales), is to stuff it with tuna and cheese. For years, and as legions of Mexicans moved from the countryside and up into the urban middle class, the nopal suffered from its reputation as a food for the rural poor. Indeed, many Mexicans' image of the nopal was of their abuela (grandmother) going off into the scrub to collect it. The memory wasn't necessarily a positive one. But now some of Mexico's top chefs are again singing the praises of nopal and working to correct its image. ''I'm always fighting this idea that nopal is a dish of the poor,'' says Sebastian Verti, a noted specialist in Mexican culture and traditions. ''I tell people, 'No no no, this is an imperial dish, it was found on the finest table of Montezuma.' '' In his book, ''Mexican Traditions'' (Grupo Editorial Diana, Mexico City), Mr. Verti lists the nopal as one of ''Mexico's natural gifts to the world'' - along with corn, the avocado, chocolate, and the poinsettia. The nopal also plays a central role at El Tajin, one of Mexico City's top gastronomic restaurants. Owned and operated by Alicia Gironella De'Angeli, a renowned cooking teacher and worldwide promoter of Mexican cuisine, El Tajin features nopales in a number of its dishes, from nopal and mushroom soup to stuffed nopales to nopal ice cream. ''It's true that for many years the nopal fell out of favor and was scoffed at as a food for the humblest classes, but [my mother] has worked hard to change that thinking,'' says Monica Gaspar de Alba, Gironella De'Angeli's daughter and her assistant at El Tajin. Not only was her mother one of the first Mexican chefs and cooking teachers to promote the use of traditional foods like the nopal, Ms. Gaspar de Alba says, but she has also exported that interest as she takes her cooking classes abroad. ''She took nopales with her to the Hotel Bristol in Paris, and has done the same for her classes in Spain, Israel, Venezuela, and New York.'' So how soon is nopal likely to become as common in US supermarkets as avocados and corn tortillas? Benito Munoz, who heads up a union of 182 Milpa Alta nopal growers, says his group as well as government agriculture promoters are working to make that day a reality sooner rather than later. ''We're already exporting 14 tons a week to Puerto Rico alone,'' he says. Researchers are studying new methods of de-needling the nopal leaf - a labor still performed by hand - and improvements to long-term conservation. Also under study are pharmaceutical and industrial uses for the nopal - nothing wholly new, since even in pre-Colombian times the people of Mexico used nopales to make paint and in adobe construction. ''We're excited about some of the advanced technological uses we think can be made of the nopal,'' Mr. Munoz says. ''But of course that doesn't mean we intend to neglect the gastronomic role,'' he adds. ''Nopal is still a food first.''