Fortunately, the Mexican supermarket in Cleveland sells the dried flowers, so I am able to make it here at home. Today I made a couple pitchers of "agua de jamaica".
Here's the recipe. Rinse one cup of "Jamaica" flowers. Put in a kettle with 4 cups of water, and bring to a boil. Remove from the heat and allow it to stand for 2 hours. Strain the liquid into a pitcher (discard the flowers), and add 4 more cups of water. Stir in the juice of half a lime and one half cup of sugar (up to three quarters cup of sugar if you prefer it sweeter). Refrigerate and serve cold.
It is not only a delicious, refreshing beverage, but it is very healthy too. "Jamaica" is rich in vitamin C, and it is supposed to be good for blood pressure.