Preheat the grill to medium-high heat.
In a small bowl, combine the olive oil, lime juice, minced garlic, chili powder, salt, and pepper. Mix well to create the marinade.
Place the shrimp in a shallow dish and pour the marinade over them. Coat the shrimp evenly and let them marinate for about 15 minutes.
While the shrimp are marinating, prepare the salad. In a large bowl, combine the mixed salad greens, cherry tomatoes, cucumber slices, and red onion. Toss gently to mix.
Grill the marinated shrimp on the preheated grill for about 2-3 minutes per side, or until they turn pink and opaque.
Remove the grilled shrimp from the heat and let them cool slightly. Cut each shrimp in half lengthwise.
Arrange the sliced avocados on top of the salad mixture, followed by the grilled shrimp.
Garnish the salad with fresh cilantro.