This is a little limited, as almost all of my experience comes from Chile. My top choice for silly as you describe it is divertido/a. It isn't so great for speaking about goofiness, but it does speak to sense of humor or playfulness when used to describe a person. Thinking back on people I've known who are that way, this was the word most often used to describe them.

Says the Diccionario de la Lengua Española from the Real Academia Española (http://dle.rae.es/?id=E0pO7wd):

divertido, da Del part. de divertir.

 

1. adj. Que divierte.
2. adj. Alegre, festivo y de buen humor.
3. adj. Arg. y Perú. Ligeramente ebrio.

This is a little limited, as almost all of my experience comes from Chile. My top choice for silly as you describe it is divertido/a. It isn't so great for speaking about goofiness, but it does speak to sense of humor or playfulness when used to describe a person. Thinking back on people I've known who are that way, this was the word most often used to describe them.

Says the Diccionario de la Lengua Española from the Real Academia Española (http://dle.rae.es/?id=E0pO7wd):

divertido, da Del part. de divertir.

1. adj. Que divierte.
2. adj. Alegre, festivo y de buen humor.
3. adj. Arg. y Perú. Ligeramente ebrio.