1. In a medium bowl, combine cucumbers, yogurt, garlic and dill and mix well. Cover and refrigerate at least 15 minutes or up to 6 hours.
2. Preheat gas grill to medium-high. Rub salmon with olive oil and sprinkle with salt and pepper. Oil grill and cook salmon, skin side down, 4 to 5 minutes. Use a wide spatula to flip salmon; grill until just opaque, another 4 to 5 minutes.
3. Season cucumber salad with salt and pepper and serve alongside salmon.