Yup.

Interestingly enough, we were just in MEX and the hotels (both Marriott brands) were reserved at a rate in USD (which is, IME, a weird thing, as my experience, even at US brands, is the rate is always given and reserved in local currency of the hotel, then I'm given a choice at checkout if I want to pay in local currency or USD). This time, like I said, the rate (at Le Meridian Mexico City and Courtyard MEX airport) were both given in USD (although other Marriott brands which I was not familiar with, likely brands that are primarily Latin American brands) were showing rates in MXD.

Always at the hotel, I'm asked if I want to pay in local or USD, to which I always say local. Chase's conversion is much much better than anything you'll ever get by paying USD at the local merchant/hotel.

In my case, I forget what the local MXD rate was I paid (and unable to download folio on Marriott's site, but I just requested it), the total I was charged on my CSR was ~US $14 more than my reserved USD rate, so roughly +2%. My Courtyard stay was actually ~US $15 less on my CSR than the rate I agreed to in USD, or about 7% less, then when I reserved on 1/31, the rate was $227.27, incl. tax, and was billed at 3412.31 MXD on checkout on 4/6. I guess it works out ok sometimes. However, I suspect both rates would have been lower if booked at MXD at booking. Not sure why Marriott chooses to book their international brands in MEX at USD rate, then swap with local at checkout, given they don't do this elsewhere (IME), but I suspect they make more $ using this method, at our (guests) expense.