Step 1Combine the rice and 1 1/2 cups of water in a saucepan. Bring to a simmer, then reduce the heat to low. Cover and simmer until the water is absorbed, 15 minutes. Remove the rice from the heat and let stand, covered, for 10 minutes. Fluff the rice with a fork and let it cool to warm.
Step 2Grill the corn on outdoor or indoor grill until all sides are lightly charred, about 15 minutes. Keep turning the corn so it will cook evenly. When the corn is cool enough to handle, cut the kernels from the cob.
Step 3Toss together the rice, corn, tomatoes, zucchini, green onions, cilantro, and escarole in a serving bowl.
Step 4Combine the vinegar, sugar and garlic. Pour over the vegetables and rice and toss lightly to mix evenly. Season the salad with salt and pepper to taste.