A lack of viable alternatives is not surprising. The reason: RMUNX has a substantial number of bonds, both PR and tobacco considered high risk and thus most are under investment grade (called Junk Bonds) that pay higher yields. When PR bonds started getting into trouble, the portfolio mix of RMUNX went from ~75% being investment grade to violating that historical positioning and having too many under investment grade. Consequently, RMUNX went from being a high-yield, moderate risk to a high yield, high risk investment. It all goes to your tolerance for risk, i.e. what you can afford to lose.
Don't own RMUNX anymore, but if you go back in their dividend history (should still be on their site), you will see dividend rates have varied over time (up and down). I suspect the recent decline is due to their bond mix, likely associated with a minor change in their bond portfolio, either from redemptions or some bonds having reached their maturity date and replaced with lower-yielding bonds (possibly of higher quality thus lower yield).
PR still needs to be resolved. Congress has signaled a willingness to provide some platform for coordinated negotiation of a settlement with the various creditors to reduce their debt, but not a change in bankruptcy law relating to U.S. Territories, and not any intervention that will cost taxpayers, e.g. a financial bailout of any sort. Consequently, a haircut is coming to deal with $70B+ of their debt and another $28B projected over the next 5-years if nothing is done. Any intervention will likely include some independent oversight to manage major "structural" changes to the territory to give it some chance of recovery moving forward. This will come sooner than later because PR, having defaulted several times already, is locked out of the debt market and is heading towards chaos - an embarrassment to the U.S. RMUNX has already (via the market) re-priced its PR bonds. The question going forward will be whether those re-priced levels will hold up when the negotiations are finalized. With a bloated government whose employees making about twice what the taxpayers funding them are making and somewhere between 60%-70% taxpayer avoidance rate in play, Margaret Thatcher's quote is very appropriate: "The trouble with socialism is that eventually you run out of other people's money". Ask Greece, Venezuela and now Puerto Rico.
As I owned RMUNX for many years, I remain distantly curious on its performance. Good luck going forward.
Aside from a difficult FX year, the Company took a one-time 4th quarter Venezuela hit to change its accounting for a country with out-of-control inflation of its currency. Without the one-time charge, the PE would be around 20x earnings. This will correct as the year progresses finalizing in June 2016. At that time, it will have one of the lowest PE Ratios in the staples group.