A "cheap" Chinese C/G was perfectly fine for me to pick up the basics for a few months before deciding to spend more money on a decent instrument. I would not buy a new one though as they will devalue greatly, and I'd recommend a 30 button model.
I have to confess to being reasonably impressed (to my surprise) with the Chinese built, accordion reeded, Scarlatti 30-key anglos which the East Anglian Traditional Music Trust bought as a teaching/loan set for beginners. They worked well enough for, as you say, people to pick up the basics and decide whether the anglo was the instrument for them or not. They tended to be on the quiet and slightly sluggish side, but overall not too bad compared with some of the cheap Chinese instruments around.
However, the prize for the worst concertinas I have ever come across has to go to the old DDR 'Scholer' instruments which were truly dreadful.