Is ballooning items in an assembly reserved for just the ISO view or is it appropriate to have them on any view so long as they are clear? Is there a standard somewhere for this?
If working to ASME Y14.100 series then Y14.24 may have a little information but honestly assembly drawings aren't well covered by the standards.
That said, the examples in Y14.24-1999 don't even show iso views let alone have balloons on them.
So yes they can definitely go in orthographic views including sections & details etc.
I want to say they shouldn't primarily go on ISO views but I think that's just prejudice on my part that I can't necessarily back up from the standards. Also, in case it's of interest, an assy view shouldn't consist of solely exploded views - see previous threads on that topic.