Wow, thanks for all the advice, everyone, I really appreciate it! I was reminded of the time I was taking a hike with my dogs a few years ago. I had with me an old box camera I picked up for a few dollars at an antique store when I ran into a best-selling author hiking with *her* dog. She stopped me because she was curious about the camera, and she wound up letting me take a couple photos of her and her dog. So I'll be sure to make my camera a little more obvious next time I'm out and about (I usually keep it in my purse or a camera bag).
I did ask a few acquaintances if they'd consider posing for me, and they said yes! So it looks like I'll be able to practice portraiture this summer after all.