... if you are limiting your cruising to the Exumas, I'm not sure I'd bang my head against the wall too much about WiFi ... it seems to me all the best islands we like to anchor > Shroud, Hawksbill, and the many small Cays, etc. there's nothing there, no homes, no internet. And most the signals you can get where it is more populated are now password protected, so unless you're good at hacking, I'm not sure I'd bother. Most places are now charging > like the Park, Staniel Cay and G'town.
It just depends, if the Internet is important to you, an inexpensive antenna would probably be nice. Are you more apt to spend most your time in the social spots like G'town, or will you want to be alone at Conception with nothing else around ? I've seen plenty of boats drop the hook, put the antenna up, and 20 minutes later move 1/4 miles down the beach looking for better reception. The Exumas are pretty popular, most the WiFi that is there is private & protected, cruisers have been mooching for years and the locals have figured it out. We've been in & out of the Bahamas for years now, spending 3-4 months a year there and I have not yet caved in for an antenna, although it's on the list ! And I can always find access on shore whenever I need it, but I don't need it that much, I do use a SAT phone for text emails couple times/day. If you think you'll spend the winter in G'town playing volleyball, taking yoga and going to pot-lucks, and you want/need to spend a couple hours a day on the Internet every day, then I'd say an antenna would come in handy there, you will be able to get a signal most anywhere in Elizabeth Harbour. And if the Abacos were your winter cruising area, the antenna is a must.
The system on my list is the Air802 with a wireless router option.
Good luck and have fun, cheers, John