We just returned from our trip and the only advice I would give is ...we found it easier to pay in pesos. It was much less confusing and cheaper. We did not over pay when we had pesos and our travel money went a lot farther. They like getting US currency but unless you are a math wiz and enjoy the challenge it helps to carry pesos. We did not exchange at home before going and ended up exchanging at Electra ( an appliance store with an exchange house toward the back of the store) in downtown across from Mango cafe. The rate was 11.70 the week we were there. Not great but better than 10 to 1. You could also exchange at a small store on Hidalgo street for the same rate. The ferry terminal at Puerto Juarez had an exchange window and there it was 12.30. But of course we missed that one going over. You can also use your debit card at the ATM at the grocery store and you get that in pesos, but our bank charges a small fee for use of outside ATM machines. So that was of no savings to us. We would just suggest changing money ahead of time at least $100-200 for meals,drinks cabs etc. It depends on how much you think you will be spending. We are not big shoppers so our expenses were limited to food, beer, and fun. You don't want to go over board because the idea is to go home with no pesos..