As members of the family Locustidae, grasshoppers, like the plague of locusts they are, can destroy your vegetable garden, flowers or grass crop in frighteningly little time. There are over 1,000 species of grasshoppers in North America alone, all of which like to eat tasty greenery--and almost all greenery is tasty to the grasshopper. If you are worried about the health of your children and pets, harsh insecticide should not be used to repel grasshoppers; there are natural alternatives.
Acquire natural predators. If you have an indoor/outdoor cat, it will be a powerful weapon in your antigrasshopper arsenal. Cats love to catch and eat grasshoppers. If you live outside the city limits or are allowed to have a small number of fowl on your in-town property, buy some from a breeder or at a local poultry swap. Chickens, guinea fowl and ducks all love to catch and eat grasshoppers, and can also provide free eggs in exchange for the free food.
Plant a barrier. Grasshoppers do not like horehound or cilantro, and planting a barricade of either herb around the plants you want to protect will keep the grasshoppers at bay. Planting calendula also works.
Spray your plants with garlic oil. Garlic oil is a good grasshopper repellent. Mince three cloves of garlic and stir the bits into an ounce of mineral oil. Allow it to soak for at least a day before straining out the garlic. Mix one teaspoon of fish emulsion (natural fertilizer found in most garden stores) with one cup of water. When the garlic/mineral oil infusion is ready, slowly blend the two into a glass jar and tighten the lid. When you're ready to spray your plants, mix two tablespoons of garlic oil per pint of water and spray. The oil will keep for a year.
Drown the pests. Mix one part molasses with ten parts water. Bury several glass jars at least halfway into your garden area. Fill the jars two-thirds to the top with the molasses/water mixture. The grasshoppers will be attracted by the sweet molasses, hop in to take a sip and drown. Remove the dead grasshoppers and refill the jars as needed.
Brew coffee repellent. Brew a pot of coffee at least five times stronger than is drinkable. Allow to cool and spray on the plants you want to protect.