Heat the grill to medium heat. Pull the husks back from the ear of corn and remove the silks. Replace one layer of the husks and soak the corn in cold water until the grill is ready. Place the corn directly on the grill and cook, turning every 5 minutes. Remove from the grill and cool until easy to handle.
Pull all the husks back and cut the kernels off the cob. Place the corn in a serving bowl.
Add the diced tomatoes, black beans, onion, jalapeno or hot sauce, garlic, cilantro, 1 Tablespoon lime juice and salt. Toss to combine.
In a small bowl, mix the diced avocado and remaining Tablespoon of lime juice. Add to the salsa and combine gently. Cover and refrigerate until ready to serve. If you are preparing this several hours in advance, place in the smallest container that will fit the salsa.