In a medium bowl, combine half the chopped cilantro, diced avocado, half the diced mango, chopped onion, the juice from half the lime and a pinch of salt. Stir to combine.
Halve the jalapeno and remove the seeds. To a blender, add the remaining mango, cilantro, lime juice, 1 garlic clove, half of the jalapeño, 1 tbsp olive oil, and 1 tbsp water. Blend cilantro sauce until smooth, taste, and season with salt.
In a medium bowl, toss the red cabbage with just half of the cilantro sauce and a pinch of salt.
Mince the remaining garlic and jalapeño. Place a large nonstick skillet over medium heat with 2 tsp olive oil. Add the minced garlic, minced jalapeño, and cumin, and cook until fragrant, about 1 minute. Add the black beans and a pinch of salt and mash with the back of a fork. Add ½ cup water and cook until beans have thickened about 2 to 3 minutes. Transfer the black beans to a bowl.
Rinse and dry the skillet and return to medium-high heat with 1 tbsp olive oil. Spoon 2 tbsp black beans onto one side of each tortilla and fold in half. Cook until crispy, about 1 minute per side. Repeat with the remaining tortillas. Sprinkle crispy tacos with chili powder and salt.
Fill black bean tacos with dressed red cabbage, mango avocado salsa, and dollop with sour cream.