By "the cambio at the roundabout" I assume this means the RBC ATM in the parking lot across from Burger King. I always check the rates and I find the RBC cambio has just slightly better rates. Sometimes it's a bit of a pain to walk to the RBC ATM with all the locals that want to "change money" in the parking lot. FX Trader is conveneante because you can do some souvenir shopping at the Sunshine Plaza or get some groceries at the Hi-Lo.