Chinese food or a hamburger were easy to come by in the Mission District on Monday. Doughnuts or bagels? No problem. But in a neighborhood where every other storefront seems to house a tacqueria, you would have been hard-pressed to find a burrito. With leaders of the national "Day Without Immigrants" calling for an economic boycott, many Hispanic-owned businesses closed for the day in the city's unofficial Latin quarter and throughout California, encouraging employees to participate in the massive protest marches. "Today, no - no working and no buying," said Enrique Varguas, 28, who rescheduled a dozen or so landscaping...