What you perceive to be common sense, sure. One person's common sense is often radically different from another's. You keep on assuming that Naoto thinks the exact same way as you.
A car accident lasting weeks. A prepared car accident. Meticulously.
In which you are planning to get kidnapped by a proven murderer. By itself, that's kind of a sign that you're not thinking that clearly. Honestly, at that point, I'd say Naoto was getting desperate. You kind of would have to be to even consider something like that, and the fact that she wasn't that emotionally stable to begin with wouldn't be helping matters. All this adds up to somebody that I wouldn't blame for not being completely rational.
I'll note that you completely ignored the rest of my post. Besides, the other posters after me basically nailed it- she probably thought she had more time and got caught off guard, which really wouldn't help. Honestly, cameras would be one of the last things I set up, in order to both avoid the possibility of inadvertent detection- should the culprit be scouting the place (it's pretty easy to avoid looking suspicious when casing a location if you know what you're doing), and to minimize the amount of redundant and irrelevant footage.
Also, do we know exactly what Naoto was doing to prepare? How long those other preparations would take? How she would obtain these cameras and how long that would take? (you're not exactly going to find effective, easily-hidden surveillance cameras in Inaba) What she had considered and dismissed for X reason (she could have considered cameras and then dismissed them for a reason that seemed perfectly natural to her)? The answer to all those questions is "No". There's a whole bunch of variables you aren't considering here.
But heck, let's ignore ALL OF THAT. The fact is that it was a mistake that was necessary for the plot to keep going. And in the opinion of the writers, having Naoto take that action would have lead to a climax that would have been less satisfying than what we got. I mean, you can disagree, but I'd argue this is less of a mistake and more of a "conscious plot design choice".