After more thought, I've decided to keep the 2MB plan for $5 a month. So far, according to my bills, I've only ever used ~50KB, so won't likely will be going over that usage anytime soon. But, should I need it, such as to get a map if I get lost, I'll have it there. And as KiltedTim has pointed out to us all, I'm not supposed to be discussing any of this on this forum, since I'm using a jailbroken iPhone on T-Mobile. So, I guess we should end this conversation.
But one last thing, thank you to everyone who was helpful here to me.