on TMobile, who make it very easy to unlock their phones for international travel, but don't offer international roaming packages. they do have Wifi calling, but then I've got skype and Piranha for that!

well, no more responses on the Bahamas, and we're off this week. Looks like Truphone has best rates among my sims, $1.66/min, and will use roamline in We3G mifi thingie for data, at Euro 0.89/MB.
Mostly, beach or wifi at those prices!

Update on Bahamas:
Roamline didn't work at all

Truphone: couldn't use phone, contacted their customer service who got back quickly to say that you have to use call-back protocol, *100*plus number
Their website doesn't mention this! But it did work....
Data also worked. Rates turned out more reasonable than I had feared.

Piranha: worked for phone, though very expensive; but no data (and they don't claim to offer data there).

Roamline update: Bahamas (and Barbados) seem to have dropped from their list of covered countries in the last 2 weeks...