I think working the desk at a hostel is an awesome way to meet people. What a fitting role for you to take on as you wait for the next travel day. As for Berlin vs Vienna, I wish I had more experience to share, but I like your attitude. Try one, if it isn't awesome, go to the other place. I admire you taking on German as a language. One of my best friends is German and I'm lucky she speaks English, but I'd love to go visit her again one day. I know you're going to have fun! And Salsa?! Yeah! Never too old to learn new things (says the woman who just got a piano after decades of wanting to learn).