I've done some leg-work already, so I'll share what I've researched / decided so far:
1) I'm with T-Mobile for my carrier in the US International roaming is not an option due to cost
2) I just put in a request to unlock my phone, I have an HTC MyTouch 4G Slide
3) T-Mobile in Germany has "Xtra Triple" for 20 Euros (10 for the setup, 10/month) — A SIM card that should work in my phone and would give me a local number in Germany with SMS and Data
4) Google Voice doesn't allow International Roaming, so I've been looking at various forwarding options
I'd love to get suggestions and hear about any experiences anyone has with a similar setup. Thanks, Slashdot!"