In a small bowl, whisk together 3 tablespoons of the lime juice, olive oil, 1/2 teaspoon of the salt, pepper and rosemary. Rinse chicken breasts and pat dry; place in a bowl. Add lime mixture; rub all over chicken; cover and refrigerate at least 30 minutes or up to 12 hours. In medium-sized pan over medium-high heat, heat oil. Add chicken; cook until brown and cooked through, about 4 minutes each side. Remove to cutting board; slice into diagonal strips about 1/2-inch wide. To prepare Corn Guacamole: In a bowl, combine avocado, garlic and jalapenos; toss gently. Add corn, tomatoes, and remaining 1 tablespoon of lime juice; season with salt; mix gently. In skillet or comal over medium-low heat, heat tortillas until warm, about 1 minute each side. Place tortillas in a tortilla warmer or wrap in a clean kitchen towel. To serve, assemble tacos with guacamole and chicken at the table!