They are speaking out loud and what you say makes sense. I had the same idea, but I wanted to make sure I wasn't going off the deep end. In this department I want to be clear and consistent.You can do. There's no convention for crystal-ball speech. I wouldn't use quote marks unless they're speaking aloud, but that's just me. If they are speaking aloud, like on a telephone, then I'd probably just write it as normal.
Basically anything works if you're clear and consistent.