Place the potatoes in a large saucepan and cover with water. Bring to a boil, cover and simmer for 4 minutes until crisp tender. Drain well and dry very well.
Toss with olive oil and tajin.
Grill over medium heat, covered, for 10 or so minutes or until tender with grill marks.
To a blender, puree the avocado, garlic, lime, olive oil, cilantro, water and salt and pepper, to taste.
Serve the sweet potato wedges topped with the avocado sauce and enjoy.