Shrimp cocktail done the mexican way

Ingredients:
Sauce
2 cups ketchup
1 cup orange soda no gas
Oregano to taste
Pepper to taste
FOR THE COCTAIL:
2 LB (900G) SHRIMP
CHOPPED ONION
CHOPPED  TOMATO
CHOPPED CILANTRO
2 AVOCADOS
SALT
GREEN LIMES
OLIVE OIL (IF SHRIMP DOSENT AGREE WITH YOU)