r is used for an approximant in English by a number of well respected phoneticians including Daniel Gimson John C Wells and Peter Ladefoged As long as the discussions defines what is meant by r thats perfectly acceptable and as long as only English is under discussion its not ambiguous But if both English and Spanish are under discussion of course you dont want to use r for both English red and Spanish rojo because that would be very confusing Its the same with Irish and Hungarian  as long as only Irish or only Hungarian is under discussion theres nothing wrong with using  for their respective palatal stops however different they may be But if youre discussing both Irish and Hungarian of course youll want to be more specific about their relative places of articulation