I've stayed at the Sheraton Four Points and the Sheraton Isabelle and they were both in USD and I paid the exact amount that was on my reservation. And actually, I forgot about the Canopy/Hilton in Cancun they did that high conversion too. It's sort of hit and miss. The Hilton Hampton in CDMX was exactly the same as my reservation. Marriott in Chiapas was booked as pesos so no issues with conversions there, but I had other issues. Good luck.