Just curious..... why do you want to go to Vienna?  I've never been to the clubs in Vienna, but from what I understand they cost quite a bit more than the FKK clubs in Germany.  Maybe someone else will chime in.

If you are leaving from Berlin, Artemis is right there.  I've been to Artemis a couple times and enjoyed myself both times.  
Also, Frankfurt would be easy to get to/from via rail or a flight and would be better in my opinion than Vienna.   You can visit Sharks (my favorite) and Oase in the Frankfurt area.

You will not have a problem not speaking German.  All the girls speak English in the clubs.

I've never rented a car before.  Germany has an excellent rail system that usually runs like clockwork and is easy to navigate.  Only you can decide whether you want to have a car.

Flyguy, Thanks for your thoughts.  Good question.  I chose Austria before I realized I wanted to take advantage of the FKK clubs.  Based on your post I will rethink my iterinery.  Possibly stay and extra day in Berlin and enjoy the club you recommended.  From some other posts I have noticed there will be a law change in Germany effective July 1st.  Since it is a little uncertain as to the effect of the change I was thinking a couple days in Austria may be worth the extra costs of the clubs there.  I would be disappointed if I spent some time in the German clubs and bbbj was not available.

I agree with the FRA area clubs, Sharks also my fav and is a usual stop for me when I visit the region, however, I have been concerned with the law changes. I asked a couple of the gals I've gotten to know and they don't think that there will be changes right away, however, as mentioned by Icebear before, some gals will likely use this as an upsell opportunity. But they also felt that most clients wouldn't bother with the upsell and risk...and gals may not make as much. The "tourist" crowd esp. from the US will still consider the upsell a bargain compared to what they pay at home.  

I will be also be looking to Austria as a alternative option, but will be seeking the advice of those seasoned members of this board to help with that insight.  

I will add that for me, recently I've stopped relying on Taxi's and public transport for a rental car. Maybe not as cheap as the bus and train but definitely gives me more freedom and access, and Google maps works perfectly there.

I've been lucky enough to have had 2-3 business trips to Germany and Austria for about ten years, so I've had opportunity to sample a lot of different types of offerings in both countries.   I can confirm what others have said about Austria.  It's definitely more expensive for pretty much the same quality of experience.  Also, the options are much more limited.  In Vienna, there are only three FKKs in the entire city.  In Germany, there seems as if there are three FKKs on the same block in a lot of cities.  I've not tried it in Germany, but the FKKs in Austria will sell you the generic Viagra gel for EUR 10 a pop.  The "flagship" FKK is Goldentime, accessible by S-Bahn.  The optics are similar to Artemis, but it's a much smaller establishment.  It has a outdoor area which is great on a warm summer evening.  Lesser-quality FKKs are Funpalast and Fresh.  Other unique places in Vienna are Maxim (a combination strip club and brothel) and Babylon, which is a high-end elegant brothel in which you can have a full-course dinner with your chosen one before heading off to the room.  Be prepared to spend about EUR 500 at Babylon.  There are tons of studios and laufhauses.  The studios usually have 3-4 girls and are barebones places.  If you're really adventurous, you can dive in without a raincoat for a small upsell.  Laufhauses are basically indoor red light districts.  

Berlin pretty much has everything you would want to try.  I would save the money you're planning to spend to go to other cities and spend it on the girls.  Berlin has a top-notch FKK (Artemis) and a couple of flat-rate clubs.  (I've been to Airport Girls.  The girls aren't as attractive as what you would find in Artemis, but, my experience is that they enjoy sex a lot more.  There are a few sex parties/gangbangs.  I've been to a few, but certain guys who are veterans to this scene can shut out the visitors.  For the GBs, you need to be comfortable with public sex and sharing a large bed with 2-3 other couples.  There is also a streetwalker scene which is worth a look just to blow your mind.   The U-Bahn and S-Bahn will get you to all of these places.

I know I approached this from a cost and availability point of view.  Given that you are also traveling for vacation to Vienna and Munich, you certainly can't go wrong in any of those locations.  I've pretty much hit everything in Vienna.  There isn't a lot in Munich itself, so you will definitely need a car.  There is an FKK Coliseum in Augsburg, about a hour's drive from the Munich airport.  It's in the Artemis class.

Bring a fully-loaded ATM card and get plenty of sleep!

your choices are Berlin, Munich, and Vienna.  I've visited all three cities.  All three cities have decent options.  Vienna can be very pricey.  Most places in Germany seem to charge about the same and are less expensive than Vienna.  Berlin has everything that you could imagine.  There are several "hidden" places in Berlin that take a little research to find and can be a little tricky to locate -- even for taxi drivers.  If I were in your shoes, I would visit Artemis in Berlin.  Artemis has everything that you could imagine: a gym to work out, tanning beds, 2 movie theaters, an outdoor swimming pool, hot tubs, saunas, bars (indoor and outdoor), an ATM, and an easily accessible location.  Multi-levels (obviously), rooms inside and outside, as well as on every level.  People will be having sex right in front of you.  Very interesting experience.  They also have lockers for all of your stuff (at no additional charge), which could fit a suitcase.  Artemis used to be off limits to foreigners, but that isn't the case anymore.