ORIGINAL: RCKen
You can use CA, or wood glue. Either one will do fine. You don't need to use epoxy as that will just add extra weight.
Ken
I prefer wood glue for everything like that, but Ken is right - either will do well. Just one word of caution with the CA. Don't get the CA anywhere near sheeting when repairing. If you sheet anthing with CA you will end up with ridges at the joints after you sand. This is because the CA sands much slower than the balsa.