Could a chronic bad taste in my mouth be a sign of cancer?

No: Chronic bad taste in the mouth is usually a result of sinus disease, gum disease, or acid reflux (stomach acid coming up into the mouth.) medications can cause this, as can nutritional supplements. Zinc deficiency can also cause this. Very rarely, cancers of the mouth or throat can cause a bad taste in the mouth, but other symptoms would be expected.

Yes but: Yes but more likely to be due to low grade infection.