Lightly mist tortillas with oil and place directly on hot grill. Grill for about 1 minute on one side, flip and continue for one more minute. Watch them because some grills are hotter than others! Remove to platter.
Spray a grated pan with the oil and place on the grill. Lightly spray the fish and place on the pan. Grill for about 1-2 minutes and then flip and continue grilling for about 1-2 minutes more or until fish is cooked through. Remove to platter.
Place tortillas on plates, top with radishes, fish, cilantro and avocado and serve with lime wedges.
Notes
You can also use this same technique for other kinds of fish. Mahi mahi is particularly nice in tacos.