In a small bowl, combine the orange juice, olive oil, lime juice, lime zest, agave nectar (or brown sugar, if using), garlic, oregano, chili powder, and 1/2 teaspoon salt. Pour the mixture into a 1-gallon-size resealable bag. Add the chicken breasts, chicken thighs and steak and refrigerate for 4 hours, turning the meat occasionally. Put a grill pan over medium-high heat or preheat a gas or charcoal grill. Remove the meat from the bag and season with salt. Reserve the marinade.

Grill the chicken breasts for 6 to 8 minutes on each side and the chicken thighs for 8 to 10 minutes on each side or until cooked through. Grill the steak for 5 to 6 minutes each side for medium-well. Allow the meat to rest for 10 minutes before slicing.

Meanwhile, put the marinade in a small saucepan and bring to a boil over medium-high heat (in order to kill any bacteria). Boil for 5 minutes until slightly thickened. Slice the meat into 1/4-inch thick pieces and put into serving bowls. Pour the cooked marinade over the meat and toss until coated. Serve the meat in warm tortillas.