The BlackBerry international plan is just email -- a lot of other network traffic gets charged at the same $15/MB rate. If it's really important to you to have push email while abroad, then you should stay with the T-Mobile BlackBerry plan.

There's no setting (as far as I know) for limiting what sort of traffic your Android draws from the network, but rest assured that just leaving it on will incur giant roaming fees since the device is constantly updating all kinds of things in the background. Best to stick with wi-fi and no data roaming (which still allows calls, texts, and other network traffic through).