Keep in mind that the rates you see listed online as the exchange rate is the bank rate. You will not get as much, only slightly less, so the banks/cambios make a bit of a profit on every $$$ exchanged... their cost of providing the service. A good way to get the current rate is to ask here on the board.

Unless you are desperate, skip exchanging at your hotel. The exchange is very much in their favor. Example: The cambio might be exchanging for $86.50J for $1US. Hotel rate... $80J for $1US. Hope this helps.