The title of the following article posted today by CNBC uses the expression going loco with quotation marks.
(Video from CNN at 0:46)
Loco, as suggested by Dictionary.com is an AmE slang expression:
- Slang. out of one's mind; insane; crazy. (1835–45, Americanism; < Spanish: insane)
and a Google Book search suggests a limited usage of go/going loco vs go/going crazy.
I suppose the cited article used quotation marks because the expression is very informal and uncommon in writing, but is it commonly used and understood in speaking nowadays? or is it sort of old-fashioned expression?