You will need to make sure the carrier offers BB data services and you have a BB dataplan provisioned. As for the rate, it would vary from country to country and from carrier to carrier. You would need to set up your AOL in the BIS for that carrier as well I would think. Not an international expert however.
To keep your email and number, why not go with a T-Mo international plan? As long as the countries you are in have GSM service, you should be OK, at least for voice.