I will close this out for the benefit of others who have sprint service and may be traveling to Bahamas. We have sprint plans in US, and used our phones in Bahamas via their Global Roaming plan. For my HTC phone, that just meant turning on global roaming and data. For my wife's I-phone, the instructions were a bit more difficult so you should contact sprint for that.
Before we left, sprint rep said the plan would work in some larger islands, but some of BTC towers were incomparable with our newer phones. That all turned out to be wrong. Our phones worked with every BTC tower. North Bimini
, chub, all thru the exumas except in the Exuma Park - as there are no towers. Was able to get good voice service, texting no problem, and even kept up with this forum, passageweather sites. The speed is only 2G, but didn't really notice it. Cost was confirmed on my bill at $0.20 per voice minute, free texting and free data. Plus I have an underlying sprint plan I was still paying for.
Compared to BTC $0.90 per minute, it was good deal. And when you need to upload data, just find a restaurant or marina with Wi-Fi. Just need to be a patron as all we found were secured servers. No problem.