Are BMI ranges a good measure to go buy when setting weight loss goals?

Yes. Aiming to be in the "healthy" BMI (body mass index) zone is a good long term goal for weight loss. However, some persons have mainly tummy fat. For those people, being in the "healthy" BMI range may still not be good enough, because excess tummy fat may be a part of "metabolic syndrome". Metabolic syndrome can lead to diabetes, so those patients should reduce tummy fat even if BMI is "healthy".

Yes. The BMI measures weight for heeight and is a good way to see what you need to lose.