OOOH bad idea from a food safety standpoint!
I'm a culinary student, and I've learned that letting food sit out over a 4 hour period of time, between the temperatures of 4-60C or 40-140F will allow the growth of bacteria, and then it's 'not safe' anymore (you may or may not get sick if you consume it after that, but its YOUR call).
Also, you should NEVER defrost anything like meat or dairy at room temperature, it should always be a) defrosted in the fridge or b) defrosted in a sink full of running cold water.
As for the taste of frozen milk I've never personally chosen to freeze milk, and that's a good question that I think I'll bring up to one of my chefs:
Is it safe to freeze milk?
I'll get back to you when I find out. :thumbs: