Muni bond funds recently seem to have some of the steadiest preservation of capital of all the bond types that I track, in spite of the Puerto Rico implosion. PR (and VI) is a critical part due to non-state-taxability, yet muni funds such as HYD and HYMB no longer seem to report their exact tax-year percentage on their web sites (just impressionistic snapshots at inconvenient time frames). It looks like turbotax no longer lets you plug in the state-exempt amount, like 9%, in the fed input part of the process. You have to hack it into an "other subtractions" part of the state return.
In the last 365 days, most bond etf type values have converged to unchanged (last 2 years a slight gain). Exceptions were the junk bonds cratered, bank loan etfs were weak, and corp a bit soft. Treasury TLT very volatile, but along with SPY stocks netted around zero change excluding dividends. So with munis yielding 4+% and prices steady, maybe they are good even aside from fed tax benefits and a bit of state tax benefits (there isn't a "my state" etf)?