To make the shrimp: Preheat grill on medium-high heat (400°F, 200°C, or gas mark 6). In a medium bowl, mix shrimp with cilantro, lime juice, oil, garlic, salt, and pepper. Stand 2 skewers up on the counter, ½ inch (1.3 cm) apart with sharp sides pointing up, and thread on the shrimp, pushing them all the way down to 1 inch (2.5 cm) from base of skewers.
Repeat until all the shrimp are skewered, being careful to leave small spaces between each. Place shrimp skewers on a sheet pan, cover with plastic wrap, and chill to marinate at least 15 minutes, or up to 4 hours.
To make the salsa: Stir together mango, bell pepper, cilantro, scallions, lime juice, garlic, jalapeno, cumin, chili powder, salt, and pepper.
Oil the grill and place shrimp on the grate. Close the lid and cook for 3 to 4 minutes until shrimp are opaque almost halfway through. Turn skewers over to cook the shrimp through, another 2 to 3 minutes. Remove shrimp from skewers. Heat tortillas on the grill or in a microwave until hot, about 30 seconds.
Fill tortillas with shrimp and salsa and drizzle with oil.