As in all things with teenagers, it depends on how it's presented. I know with my teenage daughter, if she is in control of the Garmin and can be the first one to the cache, she loves it. If I were to have her download the positions or plug them in, log the finds or do any other "menial labor" she wouldn't like it. Her interest really took off when she made her first hide.
Her boyfriend is lazy. He only will go if he gets to sit back and watch. His first experience with caching, though, was from an over zealous teacher who made it into more work than fun.