Do you speak in Plain English?

It's an interesting topic to consider.  When you are taking an English lesson, do you speak in plain English or do you use technical language?  When you are talking with colleagues do you first think in the technical language of your job then translate into plain English to speak with a colleague from a different department for them to translate from plain English into the technical language for their department?  Are you learning plain English or technical English?  Can you speak the techncial English of your job or profession but not plain English?  Do you do the same in your native language?