Thank both of you for answering. When I went to sign up for adsense, somewhere I ran into the part that said one of the reasons people get turned down was having a presence at the site for less than 6 months. But from what I've read, many people here signed up after they'd written as few as 5 hubs and been approved.
I've also found encouragement from some answers to silmilarly-worded questions, some saying that if you aren't approved the first time just keep trying every time you write a few more hubs and eventually you'll get approved. I've decided to go that route.