Google Maps on Iphone 5 (T-Mobile)?

I'm considering purchasing an Iphone 5 from my carrier (T-Mobile). They offer varying data plans (500 MB, 2GB, 4GB, Unlimited). However, I do not plan on surfing the internet or streaming so much on the phone. I mainly want to use the phone for its Google Maps/Directions while I'm out in the city. My main question is, then: Will the maps run quickly enough once I go over the limit of high-speed data for my carrier (i.e.over 500 MB if I choose that plan)? T-Mobile provides unlimited data, but only the amount of high speed data that you pay for (I'm considering the 500 MB as I have said before). What does everyone think? Will the maps work just fine on the slower speeds once I go over the high-speed limit?

I would just start lower on the contract as you can always increase it if necessary.

T-Mobile is nice in the way that it does not require you to pay those pesky overcharges if you go over your Monthly data usage. Instead of charging you, they simply stall the speeds. 500 MB a month should be just fine for what you're describing. If you need more you can always upgrade.