I was in my local grocery store yesterday shopping for a bunch of fresh veggies. My plan was to cook them all up with some garlic, hot chiles and black bean sauce. Cruising through the aisles, I came across a big display of chayote squash. I’ve never eaten them before but the sign promised me that they are delicious. OK, I’m game. I added one to my cart.
A few minutes later at the checkout, the cashier gives me the look that can only mean, “What the heck are you doing buying obscure stuff I can’t identify, buddy?” Being helpful, I said, “I think it’s a chayote squash.” I spelled it for her. She looks it up in her computer and it isn’t there. I said, “I see, you folks have a huge display of chayote but clearly you have no intention of actually selling any of it.” I get a cold stare back. The guy behind me in line decides to be helpful. “I used to be in the produce business. That’s no chayote. It’s a guava.” I said, “um, they had a whole display over in the veggie section, identifying these as chayotes. They even had cooking instructions.” “No, no, believe me when I say it’s a guava. It’s been 10 years since I was in the business but I know my fruits and vegetables.” Meanwhile, the cashier, ignoring me, has looked up guava in the computer. It’s there. She announces, “Guava is in the computer. This must be a guava.” I know I’m beat, but I protest. “It’s a chayote. You have a whole chayote display happening in the produce section.” “It’s a guava.” “OK, it’s a guava.” At this point, she could call it anything. The line isn’t moving. I was on my way home from work and just want to get out of there.
Let me tell you that it was a chayote, and definitely not a guava. It was pretty good. I chopped it up with the other veggies and added it late in the cooking process so it would retain a crisp texture. I’d characterize it as a mild veggie with a nice texture, and a pleasant addition to my black bean dish.
27th Street 
I noticed these on sale at a local grocery. We love squash around here. I am definitely going to try one of these now.
The rule of thumb with most uncommon produce items is : If it was any good there would be demand for it and if there was demand then greedy farmers would produce lots of it, force the price down and it would become popular like say bananas or potatoes. Since it hasnt become popular there is probably a good reason for it. Most of the weird stuff you see is only marginally worth buying with better tasting alternatives at 1/4 the price. The only really glaring exception to that rule would be cherimoya. A properly ripened cherimoya is quite simply to die for even if they do cost 5 or 6 bucks for a fruit the size of a mango.
Oh I do hope you run into guava guy later and can set him straight on the deficiencies in his produce knowledge. Hopefully guavas were priced less than what chayotes would have been, had they ever thought to price them.