Poking around the VRBO and AirBnB sites you'll find very few references to naturist friendly offerings. I suspect that more owners would welcome such use, if only so they didn't have to remain clothed themselves. But it's probably a turn-off to many potential guests if it was even hinted that the option was available. And it would probably be a turn-off to the majority of owners if guests outright asked "can we be nude here"?".
I suppose I could kid around with the hosts and say something along the lines: "Your property is so secluded that it must be hard to wear clothes on warm days around here". That would probably be taken as a bit odd, yet not direct enough to trigger a give and take about whether they really use it that way, and whether we'd be welcome to do the same.
Thinking about that, how would I hint that the option was available without turning off other guests, assuming I couldn't afford to rent to just naturists? Perhaps I'd just mention in the paperwork at the time of rental that the property is completely private and though we'd normally be casual about being undressed, that we'd remain clothed unless we were told it's OK for us not to be. But that you, of course, are free to dress or undress to the level of your comfort here, anytime. I suspect some guests would tell the owners that it's OK if they're nude, but would stay clothed themselves While others might try being nude, but they'd prefer the owners not be.
At home, we have a whimsical sign posted on our patio about skinny-dipping. It sometimes triggers guests to halfheartedly ask if we actually did that ourselves. When it does, we simply say yes. That when we don't have guests over, we don't wear anything in the pool or hot tub, and leave it at that. A few guests have asked if they could join us that way, and they have. Likewise, if a family comes over, the kids want to go swimming, but drat, they didn't bring their swimsuits, we say it's OK that don't wear anything and leave it at that. Sometimes the kids get to skinny-dip, but most of the time their parents don't let them. Probably because they don't want their kids to even think that's a legitimate option.
I'm usually more direct and usually have a "Clothing Optional Zone" sign posed. But my wife usually puts it away when we know we're having guests. My sister-in-law often comes by the house to look in on things when we're away. She knows we only use the pool and tub that way, and that I love to lay out in the back yard naked. So when we leave, I remind her that she's free to use the pool and be out in the yard anytime, but that it would be a shame if she didn't take advantage of being naked there when we're gone. I don't know if she's ever taken advantage of that, but I know the kids have when we were away,. At least individually, until they left the nest.