There is a new dictionary of colloquial Spanish in the United States published by the Instituto Cervantes at Harvard University: Diccionario de anglicismos del español estadounidense.
What does it say about itself, and what is my response?
The prologue states that the terms come from oral Spanish. I believe Facebook and Twitter could be viewed as written manifestations of oral language due to their informal characteristics.
Though the prologue says that these entries are likely to be read in written texts of Spanish speakers in the United States (p. 25), I have not observed that in documents produced for public distribution or advertisements. Using these entries would depend on the type of style our requester expects of the document.
It also says, on p. 26, that it does not include entries that are widespread in the Spanish-speaking world unless they are uniquely identified with the United States. “Barista” has the same meaning in Argentina as the meaning given in this dictionary. “Rentar” is used in Mexico with the same meaning as well. There are probably others.
What would I use this dictionary for?
Since it is a dictionary of oral language, I would not use it as a resource for written documents.
It is, however, an excellent resource for transcription-translation. Often, when listening to recordings I hear words that I am not accustomed to. This dictionary would help me identify their meaning and explain it to a judge if I had to defend my transcription-translation in court. For those doing legal transcription-translations, it is excellent.
It is also useful for medical interpreters. Sometimes patients use terms we do not expect in physical therapy appointments. A quick search in this document will help us identify what they mean with less trouble.
Therefore, I expect to use it as a reference for oral language terms, but not for written language. Many of these entries are marked as regional to a specific area, and therefore would not be accepted in all parts of the United States. Other dictionaries reflect what is acceptable in written documents more accurately.
As a certified Spanish translator, I evaluate the resources I use to produce quality Spanish language translations every time. I have to be aware of the latest resources and use them appropriately.