Getting there may seem daunting, but it can be a fun adventure or you can catch a shuttle bus.
Here's shuttle info: (see more at http://www.val-gardena.com/eng/page75.html)
Every Saturday Transfer from Munich (Airport "Franz Josef Strau) to Val Gardena (S. Antonius square - Ortisei).
Information and reservations:
Bus company Silbernagl, Tel. +39 0471 706633.
Price for return ticket from airport to Ortisei: 80,00 Euro
I could have sworn there's a shuttle from Milan as well, but can't find it with quick search.
To take the train, catch a train to Verona. (This is a stop on the very frequent trains headed to Venice) It takes about an hour or so to get to Verona.
Then transfer onto a train north to Bolzano (any train headed to Austria goes through Bolzano). It's maybe 90 minutes or so to Bolzano.
The bus station in Bolzano is roughly two blocks from the train station. Shuttles run roughly every hour up to Ortisei. The trip is less than an hour and very scenic. Costs about 4-5 euro.
Verona and Bolzano are both excellent places to spend the night. You can fly in, and catch the trains to either and do a bit of sight seeing same day. Veron has a Colosseum that still functions as a stadium. It's beautiful. It's also the site of Romeo and Juliet. You can see a balcony that is modeled on the famous love scene. Molto Benne for the ladies. If traveling with wife or significant other, you can score major points taking her there. Then go to the Romeo e Jiulietta restaurant nearby. Good food, cozy atmosphere. Stay at a B+B on the town main square.
Or, train it all the way to Bolzano and check out Oetzi the ice man and spend the night in Bolzano. There's a great brew pub (can't recall the name now, but if interested, I can look it up). There's also a Mexican restaurant which was actually kind of decent... very camp. The fajitas were strange (carrots and i think squash in them) but tasty. Very funny eating Italian-Mexican in Dolomite region of Alps in a town where everyone speaks German. If you don't enjoy globalization, skip it.
There are several decent hotels in Bolzano. It's a really pretty town.
If you have any other questions, shoot me a pm.