First, it should be made clear that the MAJORITY of libertarians, of which Friedman was a champion, DISAGREE with the US embargo towards Cuba. You can go to any website of the major libertarian organizations and do a search on "cuba embargo," and find an article that condemns the almost-half-century policy.
Milton Friedman, according to his biography, "was a senior research fellow at the Hoover Institution from 1977 to 2006"(until he died). The Hoover Institution is vehemently against the US embargo towards Cuba. They have written several reports about the long-standing US policy. Do a "cuba embargo" search on their website and see for yourself.
Even outside of the Hoover Institution, Milton Friedman was a member of the advisory council for the group "Americans for Humanitarian Trade with Cuba," which opposed and continues to oppose many other restrictions that US policy places on Americans concerning links to Cuba.
Montaner, on the other hand, is totally supportive of the US embargo. In 2003, Montaner wrote a piece titled "Keep U.S. embargo on Cuba" (October 2). Just like his Friedman piece, this article is also reactionary. Montaner writes as a rebuttal to the 2003 National Summit on Cuba, which took place in Miami that year. Montaner writes that the Summit included "strategists certain that fluid relations between Washington and Havana will accelerate the end of communism." It just so happens that some of these "strategists" were libertarians. One was even from Friedman's own Hoover Institution, William Ratliff, a research fellow for the Latin region. In his article, Montaner clarifies his support for the embargo with the argument that "every time Castro strengthens his power, he invests those resources to retract the few morsels of economic freedom granted to the people during the periods of deep crisis". But he gives no examples in his article.