Temperatures in summer are from 25-35°C, from June to September no wetsuit necessary. The lowest temperature in winter is 10°C. September to December and March to June: shorty, December to March 4mm wetsuit.
There is a weather station up to date:
http://chanu.altervista.org/meteo/
From Cagliari airport by car it's 15 min taking direction to Pula. By ferry from Genova to Porto Torres (1 night), then by car to Cagliari (250 km), then 15 min from Cagliari in direction to Pula. Parking close the beach.