This Pew Research Hispanic page has lots of good info.
Jobs seem to be the driving force in people leaving and coming to the mainland, mainly to FL now.
AUGUST 11, 2014
Puerto Rican Population Declines on Island, Grows on U.S. Mainland
"……...
The Island’s Economic Crisis
The onset of an economic crisis in 2006 that weakened the already-listless Puerto Rican economy likely played a role in the island’s accelerated population decline. More recent migrants to the mainland have been found to be less educated than those who remain on the island and more likely to hold less skilled jobs (Mora, Davila and Rodriguez, 2014).
According to a 2012 report on the Puerto Rican economy by the Federal Reserve Bank of New York, “Puerto Rico’s economic progress has stalled: the Island has been operating below its potential for some time and the competitiveness of the economy continues to deteriorate.” The report cited persistently high unemployment and a low labor force participation rate, as well as heavy reliance on transfer payments such as food stamps (Federal Reserve Bank of New York, 2012).
The island’s recent economic crisis was fueled both by the overall U.S. recession and factors unique to the island. These included an end to longstanding Puerto Rican government corporate tax breaks in 2006, which led to business shutdowns and public- and private-sector layoffs.
More recently, the three major ratings agencies downgraded Puerto Rico’s debt to junk status this year, citing its long history of economic weakness (New York Times, 2014). The island’s debt burden began to grow after government expenses began outstripping revenues in the late 1990s (Federal Reserve, 2012)……"
Puerto Rican Population Declines on Island, Grows on U.S. Mainland | Pew Research Center's Hispanic Trends Project