My husband & I have 2 full days in Salzburg, we are excited about the Salt Mines & the tour of the Eagles Nest. Could we do both in a single day from Salzburg? Are both worth the day away from Salzberg with such a short visit?
First, are you talking about the Sound of Music Austrian town of Salzburg (with a 'u')?
According to the website for the Eagles Nest tour, it starts at 1:15 and runs for 4 hours. Write to David and ask him if he can drop you off at the Salzbergwerk on the way back to town (he should go right past it). The last tour is at 5 pm in the summer.
Alternative, if you come over on the bus (RVO 840, Waltzmann Express) from Salzburg, it stops at the salt mine on it's way into Berchtesgaden. For instance, the bus that leaves Salzburg Hbf at 9:15 gets to the salt mine just before 10:00. The tour takes an hour. When you got through with the tour, you could take 11:27 or 11:57 bus to the Berchtesgaden Hbf, getting there in 7 minutes. You would still have over an hour to grab something to eat at the Hbf and get to the tour start across the street.
An RVO Tagesticket, purchasable from the bus driver for 9,80€ per adult, would give you round trip between Salzburg and Berchtesgaden and use of most of the other buses in Berchtesgaden for that day. Note, the last bus back to Salzburg leaves the Berchtesgaden Hbf at 18:15.