You need a Translation of your driving licence - in Austria we get that at the car club ÖAMTC (like ADAC in Germany) - you have to find out where you can get that. We´ve never been asked for an international driving licence (which is much more expensive to get).
The traffic in mauritius is very different to the traffic in Germany or Austria - therefore a lot of people are scared at first about the way of driving of mauritian people. Sometimes it seems extremely risky how they drive, but if you take into account that the driver aren´t stubborn and will slow down if you are overtaking, then you don´t have to be scared. Sure, traffic is more chaotic, and when driving in the night, always look out for dogs who sometimes sleep in the middle of the road, but don´t be afraid. I´ve been driving many times in mauritius now, and although traffic has increased since then, I still like to drive there - on the other hand, I´m used to the traffic in Vienna, which isn´t always fun too!
As to your question where to rent a car I´m no help, as we always book our car in advance at europcar. But I´m sure someone else can help you with that.
Anyway, have fun!