OK - back from Aruba.
I was able to use my iPhone 4s on the Setar Network.
At the airport I picked up a $40 Sim Card. I Cut the Sim to the right size. (In the main Setar office they have micro sims - I did not bother since I had the cutter).
I inserted the card and entered the pin 0000.
I activated a 2 week 1 GB data plan.
I had to change the APN under the "Cellular Data Settings: to internet.setar.aw with no username or password. (without this it wouldnt work and they didnt tell me this at the airport store - did my own research.)
I had no problem reaching the 3G network from everywhere on the Island. Was able to make local calls and US calls. I used about 400mb of data in 9 days with average to heavy usage. I saved the card for next trip!