In a large pitcher, mix together the lime juice, water and smaller amount of sugar. Taste and add more sugar if you think the limonada needs it. Serve over ice.
To Make Tropical Pink Limeade: Cut the ends off 2 or 3 prickly pears (handle prickly pears with latex or rubber gloves or with tongs). Make a shallow slit down the length of each one, then peel away the thick skin; discard. In a small bowl, crush the fruit into a coarse puree, then strain the puree into the limeade mixture. Taste and add more lime or sugar if necessary.