When you are visiting this area keep in mind that it's a very poor area. You will encounter street/beach vendors. Usually, a coureous "Gracias no", will suffice. Try to remember that these folks are merely trying to provide for their families. From my experience they have always been polite and not at all troublesome. I am so fortunate living the US standard that I usually spend a few bucks since I enjoy visiting the area and knowing these warm and friendly folks. Being polite costs nothing.