Prepare the salad dressing: mix all the dressing ingredients in a small glass jar, and set aside.
Prepare the Mexican salad: In a small bowl, mix all the salad ingredients. If eating the bento box after a few hours, add the dressing. If you plan to eat the bento box after a few days, keep the dressing separate and add it just before eating.
Prepare the guacamole: In a small bowl, mash half avocado, add the lime juice, chopped red onion, chopped cilantro, and chopped jalapeno, and season with salt.
Assemble all ingredients into your bento box.
Enjoy your bento box at room temperature.