Getting There & Away
The salinas are in Salta province, but most easily reached by heading west along spectacular, mostly paved RP 52 from Purmamarca. Self-driving allows you to head onto the salt plains with a guide. There are plenty of hairpin turns, however, so be careful of truck drivers who tend to take up both(!) lanes as they wind their way up or down the mountain. Prepare to occupy the shoulder at a moment's notice.
The only way of reaching the salinas by public transportation is to jump off a Chile- or Susques-bound bus from Jujuy or Purmamarca. Check timetables carefully before doing this; on some days it’s possible to catch a bus back to Purmamarca a couple of hours later, but on other days it’s not, plus once you're there, you can't do a whole lot without your own wheels. This road does have enough traffic to hitchhike, however.
You could also grab a remise (taxi) from Purmamarca, or take a tour from Purmamarca, Tilcara, Jujuy or Salta. From the last, it’s a long day, unless you opt to overnight in the Quebrada de Humahuaca.