Gett better value for your acquisitions by using some key phrases. They might not be entirely correct, but the locals do understand them.

 SPANISH  ENGLISH
 Hay descuento en efectivo? (Does this thing) have a discount if you pay cash? 
 Hay descuento en tarjeta de credito? (Does this thing) have a discount if you pay with a credit card?
 Es en rabaja? Is it on sale?
 Hay tax free? (Is this thing) included in the tax free programme?
 Quando es el vencimento? It is valid until...?
 Puedo cambiar? Can I change it for another thing?
 Hay mayor? Is there ... bigger?
 Hay más pequeño?  Is there ... smaller?
 Talla mediana Medium size.
 La factura, por favor. The invoice, please.