You can do either. Creatine is more absorbable than previously thought, and it's fine to take it without the high GI carbs, but they can help.
Since it's best to use a high GI carb with 1/2 as much protein for your post-workout drink, that would be a good time to add the creatine as well.
That's what I do, and on my off days, I just take it with warm or room temperature water (that's suppost to help the creatine fully disolve in the water).
I also use micronized creatine, as I don't see it being any more expensive and smaller particles will desolve quicker/easier (and I heard it's not realy more expensive for the company to make their creatine micronized).