To make carne asada: In a blender combine and process garlic, jalapeno, cilantro, salt, and pepper to make a paste. Put the paste in a glass jar or plastic container. Add the lime juice, orange juice, vinegar, and oil. Shake well to combine. Place the steak in a baking dish and pour sauce on top. Transfer to refrigerate and let marinate for at least six hours.
Heat grill pan over medium-high heat. Brush the grates with a little oil. Remove steak from marinade and season both sides with salt and pepper. Grill the steak for 7 to 10 minutes per side, turning once, until medium-rare. Remove the steak to a cutting board and let it rest for 5 minutes to allow the juices to settle. Thinly slice the steak across the grain on a diagonal and then chop to ¼-inch pieces.
To make filling: Toss carne asada with tomatoes, avocado and cilantro.
Assemble and cook: Spread 1 teaspoon of mayonnaise on outside of one slice. Place mayo side down and layer with a slice of cheese and filling. Place second slice of bread on top and spread another teaspoon of mayonnaise on top. Cook until golden brown, about 3 minutes. Flip until bread is golden brown and cheese is melted, about 3 minutes.