Maybe these links from the FAQ will help. Using a BB without a BB data plan can be very problematic. Some things work, others will not. Anything that goes through RIM will not - i.e. the BB browser, email, maps, most im apps, etc.
If you just need Internet, another smartphone might be a better option for you. The BB might not be your best choice.
It is impossible to say what will work in all countries. Perhaps give us those where you need service and someone with experience there can help. How to use BlackBerry on Generic Data Plan - BlackBerryFAQ What do I need a Data Plan for? - BlackBerryFAQ