In a large 14-inch nonstick skillet combine beef, potato, 1 ¼ teaspoon pepper, and 1 teaspoon salt. Cook over medium-high heat until beef and potatoes begin to brown, about 8 minutes, stirring occasionally to break up meat. Stir in onion and bell pepper, and cook until softened, about 6 minutes. Add in garlic and cumin and cook until fragrant, about 30 seconds.
Stir in flour and cook for 1 minute while stirring constantly. Stir in chopped tomato and water and bring to boil. Reduce heat to medium-low and simmer until thickened slightly, about 1 minute. Season with salt and pepper to taste. Remove from heat, and cover to keep warm.
In a large heavy-bottomed skillet heat 1 inch of oil over medium-high heat until oil reaches 350 degrees (the amount of oil will you use vary depending on your pan size). Fry tortillas, one at a time, by folding in half and laying one-half flat in oil while holding another half-open with tongs. Cook for 30-60 seconds, or until golden and crisp, and then repeat with another half to form a taco shell. Place taco shell on a paper towel-lined plate, and repeat with remaining tortillas.
Spoon Picadillo into taco shells and top with tomatoes, lettuce, cheese, avocado, salsa, and chopped cilantro. Serve immediately.
This recipe makes 20 tacos. The serving size is 2 tacos per person.