Think of this as an update on the taco bar: Lay out a platter of seasoned, lime-doused avocado halves and bowls of toppings, and let guests help themselves.
Place beans in a bowl. Heat oil in a small saute pan over medium heat. Add garlic and cumin, and saute until fragrant, about 1 minute. Pour oil over beans, and stir to coat; season with salt. Transfer to a serving bowl.
Stir together tomato, cilantro, onion, and juice of 1 lime. Season salsa with salt, and transfer to a serving bowl. Place cheese in a small serving bowl.
Just before serving, cut avocados in half, remove pits, and squeeze remaining limes over flesh. Season with salt, and arrange on a platter. Serve with beans, salsa, and cheese.