Bring a medium saucepan of salted water to a boil, and blanch the carrots for 3 minutes. Remove from the boiling water with a slotted spoon, and refresh in a bowl of iced water. Drain and reserve. Then blanch the cauliflower about 6 minutes, drain, refresh and drain again. Place the carrots, cauliflower, cucumbers and oregano in a large nonreactive bowl.

Combine the vinegar, sugar, salt and pepper in a saucepan and bring to a boil. Add the jalapeno chiles, garlic and onion and return to a boil. Cook 1 minute longer, and pour over the vegetables.

Set aside to cool to room temperature. Pour into three 1-quart glass jars and refrigerate as long as 1 month.