I used to buy from them regularly in the late 80's and early 90's - was then dominated by the Afrikaner mafia - which are probably still there but cut back a bit and replaced by the affirmative action mafia.
SA has some of the most liberal labour laws on the planet - so if you get in just check your contract carefully and enjoy the ride.
A good friend did some consultancy work with them in SA. His observations were that they were a long way behind Europe and US in terms of all-arms doctrine and what kit to implement it with, but were very willing to learn. (And they produce some very good kit in its own right.)
I think it would depend very much on what role you might have with them - going by my friend's experience, if it's advising on what kit to use to implement doctrine then you might be on to a winner. If it is the nuts and bolts of rockets and missiles you may be up against some very competent competition.
Denel is a BEE (Black Economic Empowerment) company so it's possible you could find yourself disadvantaged if you are not black and South African.
It's a while since I had direct contact with Denel - in them far gone days they were full of Afrikaaners desperately looking to get out of the company and RSA - because they thought they could guess the tea-leaf readings! However I have a contact who will be able to give us an immediate and pretty informed view. Before I interrogate her, do you want to PM me some background?