Ronald Reagan, campaigning for president in 1984, told voters, "It's morning again in America." How might Americans from different backgrounds judge the accuracy of his claim?

Ronald Reagan's allusion to the sun rising on the US was in reference to the economic, social, and political stagnation of the 1970s that the US was recovering from during his first term in office. The 1970s was a pretty rough decade for the US. Nixon had been impeached earlier in the decade, the Vietnam War had divided the country and caused a rift internationally, and the country had endured an energy crisis and economic recession. His reference was meant to signal how things were looking up and would continue to do so.
But your question asked how specific groups would respond to this claim, which is difficult to answer because groups don't think in unison. Reagan's deep cuts to social programs hurt many people, not just minorities. His belief in a smaller federal government also made minority groups wary. Similarly, his determination to prevent the spread of communist revolutions in the Western Hemisphere also brought sharp reactions, both for and against.
One can look at the polling data and make conclusions about groups' opinions, but that data would also leave many things out. For example, Reagan was the first president to nominate a woman to the Supreme Court, which he did in his second year in office. He also expanded the military, which historically has seen a disproportionately high number of blacks relative to their total population. Reagan had a mixed record with Hispanics, but in 1986 he granted amnesty for three million illegal immigrants, most of whom were from Latin America. Granted, your question asks about 1984, but there was a big shift in opinion following the amnesty. Had that amnesty occurred two years prior, the 1984 election would have likely seen even more Hispanics vote for him.
As with any president, Reagan's record would likely be a mixed bag. Although one could guess what Americans from different backgrounds would say regarding his "morning" comment, it would have to take into account that a high variability exists. No group has a singular, monolithic opinion.
http://archive.boston.com/news/education/higher/articles/2004/06/11/reagans_legacy_among_minority_groups_conflicted_complex?pg=full

https://ropercenter.cornell.edu/1980PresidentialElection

https://www.statista.com/statistics/238600/gdp-per-capita-growth-by-us-president-from-hoover-to-obama/