1. Cortes' motives to write about Tenochtitlan is very political in nature. Cortes is known to be a conquistador and it is in his great interests to have some form of power in this discovery. Seeing how wealthy Tenochtitlan is, he is awed and impressed at all the rare sights. He wrote embellished letters about Tenochtitlan to Charles the V to encourage the kingdom to conquer this great Aztec empire and probably provide him a very suitable rank or position as its discoverer.
2. He chose to write topics about food, houses, shops, and temples because it is what became prominent to him when he visited. These are the sights that he wants to enthrall the king with.
3. Ultimately, Cortes' intended audience is the King. King Charles the V is the one he wants to reach through his letters in high hopes that the king will be moved to conquer the Aztec empire of Tenochtitlan.
