If you can cycle, there is a good cycling path network in the Wachau region for spending a few days cycling in the region. This cycling path network includes Krems as well. During my trip in June 2007, I saw a lot of people doing cycling trips around the region, probably because of the nice weather of summer :)
Driving to Krems and surrounding Wachau region by car is a good way to explore this area. The road conditions are good, with stunning sceneries of the hills, Danube River, lovely towns, vineyards, castles etc. It takes about 2 hours drive North-west of Vienna to reach the Wachau area. After passing by some flat land area outside Vienna and crossing the Danube River, you will soon see that the scenery begins to turn to hilly region (which indicates you are entering the Wachau region). The first prominent town you will reach is Krems followed by Durnstein (see my VT Durnstein page) and then Melk, which you need to drive across the Danube River to reach Melk (see my VT Melk page). My trip to Krems and the Wachau area was by car, thanks to Michael (VT member Globetrott) who took my wife and I on a wonderful day trip.
One way of going to Krems and surrounding Wachau area is by a cruise along the Danube River (most tourists will visit the Wachau region by this way because it is a packaged day trip).
The good thing is that everything is arranged and you get to cruise along the river, and visiting places like Melk. But the downside is that these sort of trip is usually very rush and you may not stop at Durnstein and Krems. Furthermore, it is not cheap (arount 60 Euros for adults and 30 Euros for children). I have not tried the cruise trip but if you are interested, you can see the webpage below.
I saw so many tourists on bicycles that I plan to do that.too when I come next time to the Wachau. The distances are short, almost everywhere flat separate cycling tracks right along the river, in addition to the few bridges (only near Melk and Krems) several ferries to change from North to South and back, wherever you want nice Heurige and restaurants to eat, drink and relax and no parking problems, of course. Bicycles can be hired.
The Wachau is easily reached (in approximately one hour from Vienna) by train or car.But the most attractive way to move to and within the Wachau is the riverboat. There are frequent boats between Melk and Krems with stops at all interesting places on both banks. And there are also cruises all the way from Regensburg and Passau down to the Black Sea.