Most of the use of English (T-Shirts, radio TV etc) seems to be more about being cool than actually communicating..
An example is radio..
The DJ's pepper there dialogue with English words but not when they have anything important to communicate.
"Top 10..."
"Stay in tune.." (heard that!)
and stuff like that seems to be thrown around but when they really want to say anything that they want listeners to understand they speak Japanese.
(Most of my Japanese friends tell me they dont understand ANY of the English they hear on the radio!)