Since you are using babel with the spanish option, the default behaviour is to use "Cuadro" as \tablename (following a recommendation from the RAE); however, it is also usual, and many people prefer this regardless of what the RAE says) to use "Tabla" instead. You can use the es-tabla option for babel to change the name to "Tabla":
\usepackage[spanish,es-tabla]{babel}
Another option to get "Tabla" is to use the mexico package option
\usepackage[spanish,mexico]{babel}
but this option also changes the behaviour of the quotation marks and of the decimal separator (for details, texdoc spanish on a terminal).
If you want to change the name to some other string, you can redefine \spanishtablename:
\usepackage[spanish]{babel}
\renewcommand\spanishtablename{Otro nombre}
\usepackage[spanish]{babel}in your document? – egreg Nov 5 '12 at 0:05