Yes and no.
Most street tires come "pre-balanced", in that there will be a small blue or yellow dot, usually on or next to the bead, that indicates the lightest part of the tire. This mark is 180 degrees from where the cords or belts overlap, which would be the heaviest part of the tire. Theoretically, this mark is installed at the valve stem, which is the heaviest part of the rim.
This is not, however, not completely accurate. It's just a starting point. By rotating the tire on the rim, you can decrease the amount of weight needed, sometimes all the way to zero. Most shops will not do this, because it is extremely time consuming. You have to keep moving the tire/rim back and forth between the changing machine and the balancer, and adjust the dot placement as you go, about an inch at a time. Huge PITA.
Even if the mark is installed at the valve stem, you can still be off as much as 2-3 oz., and that's a lot of weights. I will usually try to get a tire down to .75 oz, or less, before I stop fucking with it.
Troy is right, it's best to get your tires balanced as close to perfect as you can, especially if your going to run at triple digits. Find a shop that has a computerized dynamic balancer if possible. These machines will not only balance the tire "top-to-bottom" but also side to side. You're not going to get it any better than that.
Oh, my answer is very picky, if you haven't already guessed.
JC