Preheat An Outdoor Grill For Medium Heat. To Make The Guacamole, Mash The Avocado In A Medium Bowl With The Juice Of Half A Lime, Jalapeno, Tomatoes, 1/4 Cup Onion, And 1 1/2 Teaspoons Of Minced Garlic; Season To Taste With Salt, And Set Aside. In A Large Bowl, Mix Together Beef, The Juice Of Half A Lime, 1 Tablespoon Garlic, Chili Powder, 1/2 Cup Diced Onion, And Cilantro. Form The Meat Into 6 Patties. Cook The Burgers To Desired Doneness On The Preheated Grill. Add A Slice Of Cheese To Each Burger During The Last Minute Of Cooking. Serve On Toasted Buns With A Dollop Of Guacamole.