On our very first trip to AC a couple years ago we walked to Capricorn one afternoon. Very LONG walk. I wouldn't do it again. Although we do walk to the Palapa Bar every Sunday afternoon that we're in town, just to walk off some of the calories from the wonderful barbecue at BC's. We also walk five miles a day at home.
Depending on the time of year, you would be able to drive golf carts to Capricorn, I don't know about Sundiver. During the day, bicycles are a good option as well.