I'm still wondering how a BananaDude in Africa can get his hands on promotional code to test drive Adwords for a while...
BananaDude, I'm sorry to say that I can't assist you on this - as I'm not aware of who is offering promotional credits for AdWords.
You can get promotional credits if you open up one of those Adwords MCC accounts. I believe they are like $50 credits and if you become a qualified Adwords professional they get upgraded to $100.
I wanted to add a clarification to the above post, if I may, to avoid future misunderstandings. Essentially, when an advertiser signs up to be a Google Advertising Professional, the promotional credits are intended to be offered to his or her potential clients, rather than to used by the Google Advertising Professional for their own account.
BananaDude, I wish you great success with AdWords, should you decided to give it a try. And welcome to WebmasterWorld - you've landed in a great place if your looking to enhance your knowledge of AdWords.
AWA