If you have a *blackberry* data plan, not just a data plan, but a *blackberry* data plan, I don't know why blackberry maps wouldn't work for you. Talk to you service provider.
Take a look in the gps subforum here. Or maybe someone will come along and point you straight to the answer. There was a time when there was no way to use maps from sd card; all apps downloaded maps on the go. I don't know if that's changed. But I guarantee if it has, you find the answer searching here on the forums.