Prepare Salsa: Process radishes in a food processor until finely chopped. Stir together radishes, onion, and next 5 ingredients; cover and chill salsa until ready to serve.
Prepare Tacos: Stir together brown sugar and next 4 ingredients. Toss pork with brown sugar mixture. Heat grill pan over medium-high heat; cook pork, in 2 batches, 2 1/2 minutes on each side or until done. Serve pork in warm tortillas with salsa.