TEP

Unsolicited plug for TEP wireless. I used one in London also. It's a wireless bubble, or hotspot you carry around with you. Looks like a small cellphone but it just connects to the cell towers and emits a wireless hotspot I can connect my cell or iPad to anytime it's turned on. I'll see later how good the coverage is. It's only about $6 per day for 100mb a day (more if you need it).
This time though I paid to have it sent to my house in Vegas so I could use it as soon as I landed in Germany--and it worked perfectly. When I get home it came with a postage paid return envelope. The company is top-notch and well run. I just can't travel without google maps and Yelp. Plus I can skype or FaceTime with it, so phone calls to anywhere in the world are free or pennies a minute at least.
I can't imagine a better or more convenient way to stay connected.