Coconuts that you buy and cut up yourself actually do naturally have a soap like taste to it.
Coconut juice and other Coconuts that are already cut up and being sold usually have some sugar or other artificial sweetener added to the coconut or coconut juice to take away the soap taste.
Also coconuts that are older typically have a more of a soapy taste to them than fresher greener colored coconuts do.
Even when the coconut tastes like soap it's still good and not an indication that it's spoiled.
The coconut when spoiled will have a very sour smell to it which would be worse than the soapy taste or soapy smell.
You could try sprinkling some sugar onto the cut up coconut to add some flavor to it and make it less soapy tasting.