Usually in tourist areas in Mexico as a country, is accepted the USD but the exchange rate is not good at all. Currently the official exchange rate is about 1 USD = 17 Mexican Pesos but if you try to pay in USD they will accept you the payment but the exchange rate will be lower than the official. I wouldn't be surprised if they take 1 USD for 12 to 14 Mexican pesos. And this is not because they are trying to take advantage of you, here in Mexico is not common to have bank accounts in dollars and you officially can't pay anything in dollars, so most of the people that accept it must likely end up selling those dollars cheap.

In conclusion they need to punish heavy the exchange rate to not lose money, for the inconvenience and hey if you have the opportunity to earn a little more, you take it.

I'm not going to the hivefest but I'm thinking it might be helpful to do a post about payments, bank notes and other money stuff that might help you.

I've never been to Rosarito, but I'm Mexican. So if you have an specific question feel free to ask and I'll try to help.