REMEMBER THE ALAMO CITY In San Antonio a prima ballerina takes the stage and beginner mariachis meet their masters November 16-18. But there’s more. Your weekend itinerary: Friday morning after ten o’clock, wander through the McNay Art Museum’s recently refurbished mansion and see “Corot to Picasso: European Masterworks From the Smith College Museum of Art.” At seven-thirty that evening be sure to be in your seat at the Lila Cockrell Theatre, where Houston Ballet principal dancers Lauren Anderson and Phillip Broomhead perform Cinderella with the San Antonio Metropolitan Ballet. Saturday from eight in the morning to one o’clock, catch the Mariachi Vargas Extravaganza vocal competition, which draws thirty students to the Municipal Auditorium stage as part of a weekend-long celebration. To get outdoors, head to the Alamo area, where dozens of mounted couriers will convene at the front of the downtown post office for the Pony Express Swearing In Ceremony (the riders will deliver mail on horseback from Goliad to San Antonio on December 1). If you’re not too tired after an evening concert with the venerable Mariachi Vargas de Tecalitlán at seven-thirty, go to the southeast side of town, where you can catch a late show at the Mission 4 Drive-In Theatre. On Sunday sleep late, go to brunch at El Mirador, and get a jump on your shopping at La Villita before the holiday season draws the crowds. (See San Antonio.)