Weather question: Places where in never gets colder than 50�F or warmer than 35�F, aprox.?

That's Zone 11, tropical. So in the U.S., you're only talking about Miami. (Honolulu is in the same zone, but less than 1million people). Start there and work you're way South. But it can only be coastal areas, because inland areas are gonna get WAY over 95 as you get close to the equator.