Combine jicama, cabbage, mayonnaise, capers, shallots, and pickle relish in bowl. Season with salt and pepper and set aside.
Dust grouper with blackening seasoning. Heat oil in a skillet over medium-high heat. Sear grouper on each side until nicely browned and cooked through, about 3 minutes per side.
Top each tortilla with cheese, followed by grouper, and topped with jicama slaw. Serve with pico de gallo on the side.