1. Preheat grill to high.
2. Husk and removing silk from corn. Place on a large sheet pan or platter (this will be used to carry all of the vegetables from the kitchen to the grill.)
3. Cut tomatoes in half horizontally and over a strainer that has been placed inside a bowl, scoop out seeds. Discard seeds but place the reserved liquid in a large mixing bowl. Take half of the cut tomatoes and place cut side up on the tray with the corn. (Note: Only half of the tomatoes will be grilled). The rest of the tomatoes that will not be grilled can be cored and diced and added to the mixing bowl with the juice.
4. Peel and cut the large red onion horizontally into six thick slices.
5. Place on tray with corn and tomatoes to be grilled.
6. Cut a head of garlic in half horizontally and place one half on tray cut side up with other vegetables. Leave skin on but remove end so that it sits up straight without tipping. Save the other half for other recipes.
7. Cut both limes in half horizontally and place on tray with other vegetables along with the half cut lemon. Both the lemon and limes should have the end slightly trimmed off so they sit straight without tipping.
8. Place the whole jalapeños on the tray with the fruit and vegetables.
9. Bring the tray to the grill and with the olive oil, brush the tops off all fruits and vegetables and place them all on the grill cut side down. (Leave jalapeños whole). Brush the tops with the rest of the oil. You only need to put a slight char on everything so only cook for about two to three minutes. Flip everything and cook for another two to three minutes.
10. Remove all grilled vegetables and fruit to the tray and turn off the grill.
11. Once cool enough to handle, cut the corn kernels off the cob and add kernels to the large mixing bowl with the diced tomatoes you diced earlier.
12. Remove the skin and core from the grilled tomatoes and dice. Add to the mixing bowl.
13. Cut the onion into small dice and add to the mixing bowl.
14. Squeeze the juice from the limes and lemon half into the bowl with a strainer to catch the seeds.
15. Squeeze the garlic out of the skins onto your cutting board and press through a garlic press into the bowl.
16. Remove stems and seeds from the peppers and dice the flesh into small pieces. Add to the bowl. Discard seeds and stem.
16. Add the remainder of the ingredients (except the chips) to the bowl and mix to combine. Taste and adjust seasoning.
17. Serve with the tortilla chips.