Start the rhubarb salsa (below) a day before you plan to serve the tacos, so the rhubarb can pickle overnight. Finish the salsa before preparing the oysters.
Make the lime crema (below) and refrigerate until needed.
Stir together the corn flake crumbs and salt in a medium bowl or a shallow dish. Toss the oysters, 2 or 3 at a time, in the crumbs to evenly coat, then set the oysters aside on a baking sheet or large plate.
Add enough oil to a large, heavy skillet to be about 1/4 inch deep and heat it over medium heat. Carefully add half of the oysters to the skillet, or fewer if needed to avoid crowding in the pan. Cook until the oysters are crisp and lightly browned, about 2 minutes, turn and brown on the second side, about 2 minutes longer. Transfer the oysters to a tray lined with paper towels and cook the remaining oysters.
To serve, put 2 of the fried oysters in each tortilla. Spoon the avocado crema over and top with some of the rhubarb salsa. Sprinkle some of the cilantro over and arrange 2 tacos on each plate, with a lime wedge alongside for squeezing.