Quite simply, they have.
As a brief terminology summary, Latin America refers to the American countries whose culture substantially descends from Romance-language-speaking countries in Europe, such as Spain or France. It thus includes North American countries such as Mexico, non-Hispanic countries such as Brazil, but not countries as the Philippines or Equatorial Guinea that are partly "Hispanic" but located outside the Americas.
So, for instance, México has condemned the family separation policy and the conditions in which immigrants are held:
The Mexican government on Tuesday condemned as “cruel and inhuman” the Trump administration policy of separating immigrant families detained on U.S. soil.
The current president himself, before he was president, also spoke out against the policy. According to the same article:
Andres Manuel Lopez Obrador — front-runner in the July 1 election — charged that U.S. authorities were expelling the children in “inhumane conditions.”
So has Bolivian president Evo Morales, who asserted that if the US cared about human rights:
And nor would it have separated migrant children from their families, nor put them in cages.
Morales seems to have come closer to the term concentration camp in other statements:
Trump está tan mal, que su propio pueblo marcha contra su política cruel e inhumana de tortura psicológica a niños inocentes en campos de detención.
Trump is so evil that his own people march against his cruel and inhumane policy of psychological torture of innocent children in detention camps.
I wouldn't be surprised if he used that precise term in some speech.
Although they aren't using the precise terminology used in the question, they're nonetheless criticizing the same thing.
As to why some countries might be more careful in their criticism or its terminology:
People in glass houses shouldn't throw stones. Anti-immigrant policies exist in some Latin American countries as well. They might be particularly leery of criticizing mass immigrant detention centers, since some Latin American countries, particularly recently, such as Mexico, have engaged in similar practices.
They might be afraid of antagonizing the US. The US has a great deal of political and economic influence in the Americas, and its leader has often been quick to pick fights. The increase in Mexican immigration enforcement has been partly attributed to this.
They might agree with those policies. For instance, Jair Bolsonaro in Brazil is unlikely to criticize US detention centers. Several other governments in Latin America have conservative or nationalistic views or an affinity for Trump.