Whisk the marinade ingredients, including ½ teaspoon salt. Put the pork cubes in a large, resealable plastic bag and pour in the marinade. Press the air out of the bag and seal tightly. Turn the bag to distribute the marinade, place in a bowl, and refrigerate for 4 to 8 hours, turning occasionally.
If using bamboo skewers, soak in water for at least 30 minutes.
Prepare the grill for direct cooking over high heat (450° to 550°F).
Remove the pork from the bag and discard the marinade. Thread the pork and bell pepper squares alternately onto skewers.
Brush the cooking grates clean. Grill the skewers over direct high heat, with the lid closed as much as possible, until the pork is barely pink in the center, 8 to 10 minutes, turning once or twice. Remove from the grill and season with salt. Serve warm.