Hi, I am a frequent visitor to the south coast (30 times) and I was out there in Jan/Feb. If you are staying at Turtle Beach you will not even be aware of the problem unless you travel in to Bridgetown along the main road. I should also note that reports of sewage being pumped into the sea to Graeme Hall won't affect you either (although I never saw any evidence of that while I was there) as you are to the east of the problem and the rides flow east to west.
Finally, we started boiling all our drinking water, but after drinking water in the south coast restaurants and having ice in drinks and still being fine, we gave up and didn't have any problems.
Not sure how well you know the area but we stayed 5 days at Blue Orchids in Worthing (near Champers restaurant and between the two main areas of the problem) and then for 9 days at Rockley Golf Club.
The areas mainly affected at on Rendevous road from the petrol station up to the CIBC bank/post office, and on the south coast road around Lanterns Mall/KFC. There is dirty water bubbling up from the manholes in the road and flowing down the gutters. It varies from day to day and I guess depends on rainfall, but it really didn't have a negative impact on our stay. I do feel sorry for the locals and businesses impacted as it shouldn't be happening, but some reports I have seen (like in the Telegraph in the last week) tat say it affects "the whole of the south coast" are just not true.
Feel free to PM me if you need any more info.