Cagliari International airport is located in Elmas, around 60 km from Villasimius where you can arrive
driving in Strada Provinciale 17.
In Cagliari airport in low season like the end of September there are chip rent a car offer. You can fly to/from Spain, Germany, Swiss, France, Poland, Belgium, England, Ceca Republic, Austria and
rest of Italy thanks low cost fly (Ryanair, Easy Jet, Lauda Airline, Austrian Airline, Smart Wings, Air Berlin, Tuifly and German Wings) or thanks international air line (like Alitalia, Air France, etc.)

In north Sardinia there are other two international airports: OLBIA COSTA SMERALDA and ALGHERO.
The distance from Villasimius is about 350 km.
In north Sardinia airports in low season like the end of September there are chip rent a car offer.

By Ferry Boat:

You can arrive in North Sardinia by ferries thanks Porto Torres and Olbia ports, or in the south thanks
Cagliari port. The chipper across is from Savona (Novi Ligure)/Genova/Livorno/Civitavecchia to north ports
because there are few ferries companies that make big offer in low and medium season in the end of
September. (look at Tirrenia, Moby line, Grimaldi, Saremar, Sardinia Ferries).

Porto Torres and Olbia are about 350 km from Villasimius.
You can make the travel reservation on line in ferries companies website or contact a travel agency.
Make on time your reservation and you can have a big discount!!!!