[GadgetKen]

Blackberry prepaid service is available on Digicel (they are now offering 1,2,4 week packages in Bermuda and also in Caribbean countries that have Digicel networks) Digicel Prepaid Blackberry service This would be a good solution for Caribbean blackberry coverage without the committment since Digicel allows some Digicel network prepaid roaming at reasonable rates, but wouldn't help much on other networks in North America or Europe where the rates would be much higher.
Blackberries can be tricked in some instances to access the web and standard email services, I've seen this done with Nextel-Iden blackberries ("Boost Berries)and Verizon CDMA blackberries (PagePlus Blackberries) in the US. Probably a similar procedure with a GSM blackberry, but you would still need some sort of data access and a good question is whether it would be worth the price. Might be worth contacting Mobal to ask if they can officially arrange Blackberry service for your device rather than the clandestine route.