I have spent the last 10 winters in Mulege Baja Sur. For the last couple years the Peso has been way down. I just checked the exchange and it's 15.73 Pesos to US dollars. That said, rural Baja is a cash society, with little credit card access.
To answer your question, I carry both currencies. The reason is the rate of exchange the store/vender gives. I have found, for example if I use US dollars at Pemex Gas Stations they give a horrible exchange rate, perhaps 12 to 1. So I always pay in Pesos.
Now at my campground, the landlord wants $9 US per day. If I offer to pay in Pesos he would only give me 14 pesos to US. Dollars. So I paid in US dollars. I personally have never stayed at anyplace who refused Pesos.
I don't know if this answers your question but to me it' all about the rate of exchange. Also if you travel in rural Baja try to use small Peso notes. Some taco stands may have difficulty cashing a 200 peso note.
It's a wonderful place to visit enjoy your travels.