500,000 may be about right.
500,000 US visitors to Aruba in one year? The Aruba Travel Bureau stats show @ 36,000 US visitors in the high season month of January, 2003, the last reported month. If the high season last five months that would be 180,000 total during the season. I doubt that the off season months (half of which is hurricane season) totals equal 75% of that number.