Even if you sign up for easy roam now, your previous pay per use roaming charges will remain.

I suggest finding a spot with wifi and you can download areas within google maps so you can use the GPS functionality without the need for data.  Just note that other online info (like business info, transit or traffic info) will be unavailable if you did this.

Hi there,

If you sign up for Easy Roam now, you will not be charged $5/MB for any additional data you use while you're abroad, but unfortunately, you will still be charged $5/MB for any data you've already used today. Easy Roam is a daily flat rate that is charged when you make or receive calls, send text messages, or use data while you're outside of Canada. Once you have Easy Roam activated, you'll be charged the daily rate regardless of how much data you use, so it can be a good option if you plan to use your phone frequently while you're abroad. Keep in mind that you can activate Easy Roam anytime while you're travelling, and you'll only be charged for the days that you use it.