Certainly you can write from anywhere in the world. But it helps to have some inspiration. Living in a major city like New York would be great for people watching. Sitting in cafes, observing and quietly eavesdropping on humanity. On the other hand, who can afford New York City? And then, sorry, but those are not the people I want to write about.
Give me a little less humanity, a more relaxed pace, and a beautiful natural world. Southern California? Do you know of any sleepy inexpensive beach towns there? Florida? Maybe, but give me a four season climate. Give me Grand Haven, where even winter is inspiring.