Peel potatoes; cut into 1/2-inch dice. In a large saucepan, heat oil over medium heat. Add potato; cook, stirring occasionally, until golden brown, about 6 minutes.
Add beef, onion, and jalapeno; cook, breaking up meat with a spoon, until beef is thoroughly browned, about 4 minutes. Add tomatoes and juice, cumin, paprika, and 1 teaspoon salt; cook until liquid has evaporated, about 6 minutes.
Heat tortillas, one at a time, in a dry skillet over medium-high heat, turning once, until lightly browned, about 10 seconds.
Leaving space on bottom and sides, layer tortillas with sour cream, lettuce, beef mixture, cheese, and cilantro, if using; squeeze lime juice on top. Fold bottom upward, covering filling by 2 inches. Fold each side to overlap, leaving the top end open. Serve garnished with lime wedges.