My wife and I will be spending four full days in Berlin (July 1-4) before traveling July 5 to Mainz to board a Rhine cruise. Would the Deutschland ticket (€49) cover all local transportation in Berlin (S-Bahn/U-Bahn/buses)? Can that be purchased in advance online or at the airport after arrival?
I'm assuming we should simply buy one-way tickets for the Berlin to Mainz trip, correct?
Deutschland ticket is valid for regional trains only (yes for Berlin area (VBB) and Rhein-Main area incl. Frankfurt and Mainz (RMV)). But travelling from Berlin to Mainz is not meaningful that way - long distance trains are recommended (minimum Berlin - Frankfurt one-way).
The price for a 24 hour ticket in Berlin is €9.90-€11.40; the more expensive ticket includes transportation from the airport to the city (ABC zones). For most sightseeing the "AB" ticket at €9.90 works. So, likely the Deutschland ticket wouldn't save you any money. You are correct regarding the Berlin-Mainz ticket.
I was in Berlin at the end of November. It was easy to purchase tickets at the airport ticket machines and at the Zoologischer Garten station. For four days you may want to use the VBB app. (I didn't bother as I was only in Berlin for two days.)
I found the DB app very helpful for checking schedules and purchasing long-distance tickets.
For local transport in Berlin, we used the BVG app to buy our tickets. Super easy and convenient.
Look into the Berlin Welcome Card, can include local Berlin transportation and museum discounts.
You purchase it online or at the TI at the airport or train station upon arrival.
