For the pico de gallo, combine all the ingredients and set aside for at least 10 minutes. For the guacamole, mash the avocados with a fork and combine with the remaining ingredients. 

Grill the sausages on a barbecue hotplate (or pan-fry in a little oil) for about 10 minutes over low-medium heat, turning frequently. (If using hot dog frankfurters, cook according to the directions.)

Split the buns in half lengthways, but not all the way through, then toast on a hot grill or frying pan. When toasted, place the lettuce leaves on the buns, put the sausages on top and scatter with cheese. Serve with the guacamole, pico de gallo and sour cream so people can add as they please.