well as you say many never use it, i know lots of people that used to use it either in a Gaelscoil or in the area they grew up , but their ability has diminished over the years from lack of use, someone just out of school will have much better Irish than someone who went through the same education but hasnt used it for 20 years.
Broadly speaking I would find the following figures, extrapolated from this report to be fairly accurate with what ive observed,
http://www.mayococo.ie/en/Services/Oifi ... 645,en.pdf 7.8% Fluent or very fluent (357,000)
19.5% Middling (893,000)
14.2% Not so fluent (650,000)
32.5% Only a little (1.48m)
26% None
58 % of the population have little or no Irish. I know many people who can only think of one or two words in Irish. I myself had almost nothing bar a few words and a vague familiarity with some prepositions and irregular verbs on leaving school.