Madeira's terrain and road networks are VERY unique and require some careful maneuvering!
Madeira's roads are some of the STEEPEST and SKETCHIEST I have EVER ENCOUNTERED throughout my 55+ countries of travel!!! Please ensure that:
a) you are comfortable driving
b) you have a solid vehicle that works properly and can take a hill
c) stick to the primary roads on your Google maps
d) if you get stuck on a back road and it's looking sketch, backtrack and get back on Google Maps' main road
e) get a small car (Fiat 500 ftw!) - many roads are winding and single-lane, parking spots are teeny!
f) drive carefully, the local drivers are much more comfortable on those hills and corners and will come atcha!