Combine first 5 ingredients in a medium bowl. Add shrimp; toss to coat.
Heat 1 1/2 tablespoons oil in a large cast iron skillet over high heat. Add shrimp and cook, stirring occasionally, 4 minutes or until shrimp are done. Remove shrimp from skillet.
Add remaining 1 1/2 tablespoons oil to pan. Add onion and cook, stirring often, 2 minutes. Add bell pepper and cook, stirring often, 4 minutes or until softened. Remove skillet from heat and add shrimp, tossing to combine.
Top tortillas with shrimp mixture, crema, and jalapeño slices, if desired. Serve with lime wedges and Mango-Lime Slaw.