Thaw fish, if frozen. Rinse fish. Cut fish into 1/2-inch pieces.
In a medium saucepan bring water to boiling; add fish. Cover and simmer for 3 to 4 minutes or until fish flakes easily with a fork. Drain fish; cover and chill.
In a medium saucepan combine broth, cumin, garlic powder, and hot pepper sauce. Bring mixture to boiling. Remove from heat. Transfer to a large bowl. Stir in tomatoes with jalapeno peppers, cucumber, yellow summer squash or zucchini, plum tomatoes, and green onions. Cover and chill for 4 to 12 hours. Before serving, stir chilled fish into vegetable mixture. Makes 4 to 6 servings.