Hey Amand,
The main transportation is bus,you can check the website at for the schedule.
I use this service everyday.It is safe and it's 5 Rupees for each trip 0600-2000,2000 onwards is 8 Rupees.
If you want to travel purpose,I would recommend to rent a car because you can stop anywhere when you feels like enjoy the great view,2 days will cover the whole Mahe.You may rent a car with a price of 500Rupees a day,you may use your credit card as deposit or pay USD900 cash as deposit.
Hope this information helps.