Pesos are king. Dollars are great for getting the blue rate which if you pay in USD for anything here, you'll be paying at the official exchange rate, unless someone else has seen otherwise. If you haven't researched Dolar Blue, you may want to begin that process. Official rate this weekend is 8.83 pesos to a dollar versus 12.65 pesos at the blue.
Edit: I just reread your message; I'm not sure about tour operators or travel agents. I think there are a few people in the travel business on the forum that may be able to respond with a better answer. My response was using pesos versus dollars in general. A cueva on Florida will likely give you a better rate than a hotel. The last travel agent I used was in May 2014. I was able to buy two airline tickets in pesos, one for me (resident) and one for my son (non-resident). The last friends that went there this year were asked to present their DNI or other proof of legal residency in order to pay in pesos. That was just one single travel agent; I'm unsure if this has progressed to other travel agents.
And the blue rate is for currency conversion, not a general rate of direct charging. You exchange your dollars at the rate based on your method. Arbolito/cueva/hotels/etc will exchange at a rate closer to the blue, meaning you get more pesos for each dollar. Credit card, National Bank, and ATM convert at the official rate. The less pesos you receive per dollar, the more dollars you are essentially paying for whatever you buy with pesos (included this because it seemed to be a point of confusion). Some restaurants will accept dollars but I believe they legally have to "charge" at the official rate, but that rate may vary per restaurant (although I've not opted for paying this way).
