If you can get ahold of a T-mobile plan and be added, that would be best, I use a t-mobile plan to go to toronto all the time and it works amazing,(not driving up to toronto) only while there does it work great, and a added line only cost $10+ tax which comes out to $15 something.
As well amazon always has the T-mobile sim for $5 or less.
And while being a T-mobile customer they offered me a few times a free sim.
But if you already went with h2o as you mentioned then...
Hope it works well...