A few of the folks that I've tried to convince to come windsurf have tried the sport before but were frustrated to death. The board they tried was hard to balance and didn't float very well. The sail they were loaned was difficult to lift from the water. They became convinced that the sport was incredibly difficult because they started on advanced equipment and didn't get much training.
Don't feel discouraged. You can start sailing on your first day under the right conditions. The beginner's class at Worldwinds involves a big board, a small sail, knee-deep water, and a good teacher. You will probably fall off the board a few times, but you'll spend more time sailing than anything else.
Based on my experience, the beginner's class will teach you how to stand on the board, uphaul the sail (that is, lift it from the water), steer the board, tack (to turn the board by facing it into the wind), and to get the board moving. Once you learn those basics, you're cut loose to practice for a couple of hours.
As long as you're in relatively good health -- you can swim, you can climb a few stairs, you can lift a backpack off the floor -- I think you can take this class. Windsurfing doesn't require above-average strength. This is especially true if you manage to learn the correct posture early. This is why you'll see skinny stick-people, kids, and retirees windsurfing right along with body-builder types.
As you learn more advanced techniques the sport seems to require even less strength. The harness class teaches you how to pull the sail against the wind by hooking it to a harness (basically a fancy belt). The beach start class will teach you one way to lift the sail by using the wind rather than arm strength. With each class I've taken, windsurfing has become easier and more fun.