For Grilled Shrimp: Whisk together the chipotle chili powder, brown sugar, cumin, season salt and pepper in a small bowl.
Place the shrimp in a large bowl, toss with olive oil and garlic. Add the spice rub and stir well to coat; set aside.
Heat grill to high.
Skewer shrimp with 2 skewers to prevent difficulty in turning shrimp.
Place on a grill to cook until just cooked through, 2 to 3 minutes per side.
For Tostadas: Toast tostada shells in oven according to package directions.
Cut avocados in half, remove seeds and scoop out pulp. In a small bowl, coarsely mash avocados and season with salt and pepper to taste.
In another medium bowl, combine slaw, jalapeno pepper, cilantro, mayonnaise, garlic and juice of 1 lime. Set aside.
Chop tomato and set aside.
When ready to serve, each person can build their tostada as they wish. Serve with lime wedges.