Whisk the marinade ingredients together in a large bowl. Set aside half the marinade. Add the diced chicken to the bowl and toss to coat.
Heat 2 tablespoons of vegetable or avocado oil in a large skillet over medium heat. Add the chicken. Cook each piece of chicken on both sides until seared and the internal temp reaches 165 F, about 6-8 minutes. Set chicken aside on a plate.
Add additional oil to the pan if there's less than 1 tablespoon left. Add the bell peppers, onions, 1 teaspoon of salt, and 1/2 teaspoon of pepper. Saute until they begin to soften, about 6 minutes. Add chicken back to the pan and toss to combine.
Assemble your salad by tossing the lettuce and cilantro together in a large bowl. Be sure to set aside some cilantro as a topping. Toss your salad with chicken and veggies, and set aside dressing. Top with cotija, and avocado slices, and enjoy!