From Buenos Aires you have to take a bus or fly to Tucuman. Santa Maria is 180 Km. from there. You have a 3-hour drive from Tucuman, or you can take a bus that will get you there in 4/5 hours.
If you go to Salta, you have a 3.5-hour drive. This is the best option. You can take also a bus, but it makes to many stops so your trip never ends.
Santa Maria is a beautiful valley with a nice weather. Best time to go is spring/summer. Sun is king there and it is an excellent place to relax and for a change of scenery.
Surrounding the town you can find many archaeological ruins and small vineyards and wineries where you can get excellent wine.
From here you can visit the Ruinas de Quilmes, an ancient Indian town, and Amaicha del Valle.