Naples, Italy:
* NAY-pəlz (The "a" in "nay" is short, like in "cat", and the "e" in "pəlz" is like the "a" in "about".)
Naples, Florida:
* NAY-pəlz (The pronunciation is the same as for the Italian city.)
Both cities have the same pronunciation, so you can use "NAY-pəlz" for both.