To make the crema: Combine the sour cream, taco seasoning, cold water, 1 ½ teaspoons lime juice, and season with salt. Set aside.
To make the pico de gallo: Stir together the tomatoes, onions and cilantro. Set aside.
To prepare the avocado boats: Slice the avocados in half the long way and gently remove the pits. Slice the bottom off each avocado half so they sit level, flesh side up, on a large serving platter. Carefully scoop the flesh out of each half, leaving about one-eighth-inch flesh on the sides and bottom. Transfer the avocado flesh to a medium bowl.
To make the guacamole: Mash the avocado flesh. Stir in 2 teaspoons lime juice, the Worcestershire sauce and half the pico de gallo. Season with salt and black pepper. Set aside.
To assemble the seven-layer avocados: Fill one avocado half with an even layer of 1 tablespoon refried beans, 1 tablespoon guacamole, 1 tablespoon salsa, 2 tablespoons cheese and 2 tablespoons shredded lettuce. Drizzle the crema on top and garnish with a pinch of pico de gallo and a few olive slices.
Repeat step 5 with the remaining avocado halves. Serve immediately with your favorite tortilla chips.