Visiting Austria and Germany in March for a week
 

We are using a timeshare in Maria Alm (Alpenland Sporthotel), to visit Austria and Germany last week of March 2011. Is it necessary to rent a car if we want to visit Munich, Salzburg and Vienna? Any suggestions on what to see given the limited time. We're hoping to just join organized tours so we don't have to drive. Where can we book these tours? Is it too ambitious to include Prague in this trip too?

How do you plan to get there in the first place? Will you use an organized transfer from Munich airport?
Munich and Salzburg are both perfectly fine day trip destinations. Salzburg should be the only one of those you mentioned within easy reach with public transport. Munich would take more time, transfers bus/trains, and is more comfortable to reach by car.
Vienna and Prague are not day trip destinations from where you will be staying.

that's a fine trip

Thanks for the responses. We're flying into Salzburg (via Frankfurt), possibly take a cab/bus or rent a car from the airport to Maria Alm. Another option: from Salzburg, join organized tours to Munich, etc. any suggestions on must-sees in Austria, preferably day trips?

The salt mine tour in Hallstatt is just outside Salzburg and very worthwhile.

Also, you could go up to Obersalzburg, where the Nazis planned to make their last stand (though it didn't work out that way). The museum there, Dokumentation Obersalzburg is excellent if somewhat sobering, and the parts of the extensive underground bunker system that are open to the public are fascinating. The Eagle's Nest won't be accessible at that time of year, but don't let that deter you.

Herrenchiemsee, one of King Ludwig's three castles - the others being Neuschwanstein and Linderhof - is just off the autobahn between Salzburg and Munich and is a nice visit involving a boat ride across the lake.

I will be in the same area only at St Johann Im Pongau 30miles south of Salzburg the Alpenhotel.
to be there 7 days. Is it too ambitious to train to Linz and the wine country of Dunstein and Melk for one day and another day trip to Hallstat. will also see the Salzburg landmarks, Mozart, Sound of Music etc. This will be first week of May 2012. Any advise greatly appreciated