Cut the peaches in half, remove and discard the pits, and chop them (you should have about 1 1⁄2 cups).
Put the peaches and the rest of the ingredients in the blender and put the top on tightly.
Turn the blender to medium to start chopping the fruit and ice. Adjust the blender to high speed and blend until the mixture is really smooth and moves easily in the blender, about 1 minute.
Serve right away, or cover and refrigerate up to 24 hours (if you do this, stir it well or reblend before serving).