About 40% of my investable assets are in in individual muni bonds and I have been buying them for my personal account for 20 years. My portfolio has more than 100 individual bonds which I have researched myself. I bought California GOs when everyone said California was going bust, I bought Illinois GOs when everyone said Illinois was going bust-- and did very well.
However, PR scares me. It has more debt per person than Detroit with a declining population. As stated, it is somewhat unclear whether PR can file under Article 9 for Bankruptcy. There is an older case I think involving Guam that says it cannot -- but I am not comfortable with that. Not only that, the zeroes are the scariest of them all because they balloon in full at the end.
My contrarian core would normally say buy some but the fear side is winning that argument. I buy bonds for safety and stocks for appreciation. PR bonds do not fall into the safety category for me. Good Luck.