At home: Drain and rinse the black beans. Pack them in a small container. Pack the corn, cilantro, salt, pepper, and lime juice in separate containers. Keep the avocados whole and unripe.
At camp: Cut the avocados in half, remove the pit, and scoop the flesh into a bowl. Add the lime juice, salt, and pepper. Mash with a fork to your desired consistency — chunky or smooth.
Stir in the black beans, corn, and cilantro until combined.
Lay a tortilla flat. Spoon about 1/2 cup of the avocado mixture down the center. Add shredded lettuce if using.
Fold in the sides, then roll tightly from the bottom. Repeat with remaining tortillas.
Serve immediately. These wraps are best eaten fresh, but they'll hold for an hour or two in a cooler if wrapped in foil.