#1 for popularity according to TripAdvisor is Su Nuraxi:
Su Nuraxi is a settlement consisting of a seventeenth century BCE
Nuraghe, a bastion of four corner towers plus a central one, and a
village inhabited from the thirteenth to the sixth century BCE,
developed around the Nuraghe. They are considered by scholars the most
impressive expression of ...
That should be manageable. Take the bus number 1 from the train station to Piazza Grande. From there it is a short walk to the terminal. The price of the bus ticket is 1.20 EUR. Schedules can be found here: http://www.atl.livorno.it
All towns will have an ATM, though it may not be accessible 24/7. I would expect most restaurants and shops to accept cards, though small ones may not.
It would be reasonable to expect to mostly use a card, but don't rely on it.
In terms of card acceptance in Europe I’d rank a few countries basically like so from most able to live just on a card to least:
Tier 1: Sweden
Tier 2: UK, other Nordics
Tier 3: Germany, France
Tier 4: Switzerland, Italy, Spain
Corsica is France though in many ways more akin to Italy. In France to a large extent and particularly in Italy you’ll often find ...