They are not diarists per se, but a few chroniclers give some insight into day to day life. Sone examples:

• Gonzalo Fernández de Oviedo, who was governor of Santa María la Antigua del Darién, and also alcaide of Santo Domingo. His most important work is "Historia general y natural de las Indias", but his "Sumario" and the "Batallas y Quinquagenas" are also useful.

• Pedro de Cieza de León, with his "Chrónica del Perú" also sheds some light into daily life.

• Felipe Guamán Poma de Ayala wrote quite an extensive "Nueva Corónica y Buen gobierno", where you can see the many mistreatments endured by the Indians at the hands of the Spaniards.

• Fray Bartolomé de las Casas in his "Historia de las Indias" also offers a good picture of the mistreatment of the natives, but he centers his narrative on it around the encomiendas and the encomenderos.

• Motolinía writes a great deal on the day to day life in the Viceroyalty of New Spain.

For the latter dates on which you are asking, I personally recommend reading the notes Félix de Azara took on his expeditions as a naturalist.

I don't know whether these sources are available in English, as I read them in the original Spanish texts, being Spanish myself.

or anything written after ~1950

Unless you plan to do your own archival research I think this is an odd restriction. Since the 70s 80s, the social turn in historical study means you would be ignoring lots of good historical monographs that would have pertinent information. Even if you wanted the primary sources those scholarly works would point you to them.