Bill,
As others have said, that is a prickly pear cactus. The red to purple fruits can be eaten raw without any preparation other than pealing the skin off off the fruit. The fruit does have tiny needles (glochids) that may be hard to see, so exercise due care in handling them. The needles are small enough that if you get them in your hand, you probably won't even see all of the needles to remove them. It's not so much painful as it is irritating. In my experience, the red fruits are sweeter than the dark purple ones. Mid to late September is the best time to eat or harvest the fruits, which have all pretty much fallen off most plants by now. The fruits can be used for everything from jelly to juice.
The pads can also be eaten, but not all varieties are equally palatable. They also should not be eaten raw, but cooked to somewhat tenderize them. The plant also has been used as a medicine for a variety of ailments.
Hope this helps.