Fresh prickly pear pads are found in gardens in April and May. They are available year 'round in Mexican grocery stores.
Prickly pear pads or nopales are a common vegetable in Mexico, as common as green beans in the U.S. They are a traditional food in Southern Arizona, brought by people who migrated from Mexio and eaten long before that for millenia by people who lived on the wild foods of the desert. Here are instructions for how to prepare the pads and several recipes to make nopales your new favorite vegetable.
You can find many recipes for prickly pear pads and fruit in my Cooking the Wild Southwest, Delicious Recipes for Desert Plants and The The Prickly Pear Cookbook.