As you can see in the image below, the SQL Server Interface language is in Spanish and I want to change to English.
I tried my best to find a way to change it without uninstalling this Spanish installation as there are databases already used by some applications in our company.
Just verifying: If I understand you correctly, you want to change the management studio (SSMS) interface language and leave the actual SQL Server language as it is.
English is supported on all localized versions of SQL Server, so you shouldn't have to install a language pack.
You might be able to use -> Tools -> Options -> Environment -> International Settings -> Language. That works on SSMS 2014 and doesn't appear on my copy of SSMS 2008, but I don't have any other languages installed.
Other users had the correct language show up after changing their Windows interface to English.
Hopefully, one of those two things will help you out.
