It also depends where you are going to stay in Lagos.
Although we have a much improved local bus service, it does not operate at night after 31st August.
If you stay anywhere outside say a 1 km radius from the city centre, you may find doing shopping and going to restaurants at night a bit of a pain, especially as Lagos is quite hilly.
In October, car hire prices are likely to be down, and the price of hiring a small Group A car for your stay and petrol may offset the cost of a private transfer each way from Faro Airport and give you extra flexibility to do things such as visit the West Coast.