I think if your conscience is telling you to abstain from blood then you should. Whether it's a "law" that everyone is obligated to keep, then no, it's not. When the decision was reached in Acts 15: "Therefore I judge that we must not cause trouble for those who are turning to God from among the Gentiles; but that we write to them to abstain from things polluted by idols, and from sexual immorality, from things strangled, and from blood. For Moses has had from ancient generations those who proclaim him in each city, being read in the synagogues from one Sabbath to another." it was a concession to improve relations between Jews and Gentiles, not impose laws on the Gentiles that they were obligated to keep. If I invited some orthodox Jews to my home to share a meal I would make sure everything was kosher; otherwise, I wouldn't worry myself.
If JWs teach this as a law we must keep, they're teaching false doctrine. That's my view.