Since I couldn't find anything on how to dehydrate spaghetti squash, and nobody here seemed to know how, either, I tried doing it myself.
First, I boiled the whole squash until it was fork-tender. You could microwave it (poke some holes in it, then microwave for 10 minutes, or until fork-tender) if you're not averse to cooking in the microwave.
Next, I cut in in half, lengthwise, and scooped out the seeds. With a fork, I raked out the strands of squash and drained them for a few minutes, in a strainer.
Finally, I spread the strands out on the dehydrator racks and dried them at 125 degrees. It only took a few hours. They look kind of like yellow Silly String.
This morning, I poured a little boiling water over them and let it sit for a few minutes (less than 5, because I'm not very patient), drained them, and took a bite. They were pretty good! They were still a bit crunchy (not like dry-crunchy, but like fresh-crunchy). I think, if you soaked them a bit longer or, maybe, boiled them for 5 - 10 minutes, you wouldn't be able to tell them from fresh.
This was so simple, and worked very well. I wonder why I couldn't find directions for doing it? Surely, I'm not the first person to think of it! If I can get more of them for a quarter each, I'll be dehydrating a lot of them.