It depends on how soon you're going to use it.
The food is already precooked, so it really has no effect if you thaw it in hot water. There are safe food temperatures, so as long as the food isn't sitting for a period of time in the "danger zone" of above 40 degrees to just under 70 degrees, you'll be fine.
That's the equivalent of above fridge temperature, to a room temperature.
As a rule of thumb, with baby food, I would thaw it in cold water and then refrigerate until ready to use. Heat it when you are just about ready for baby to eat it. Microwaving baby food isn't really a good idea, so this option is much better.
at 9:39 AM on Oct. 1, 2010