Like, was it used by Spanish speakers before the Beckhams used it?
I’m pretty sure it’s been used in the Spanish speaking world as a girls name…
That’s what I thought, as in [name]Santa[/name] [name]Cruz[/name]? Turns out there was never a female saint named [name]Cruz[/name], the translation is actually “Holy [name]Cross[/name]”.
I don’t know about saints… but I guess as in [name]Santa[/name] [name]Cruz[/name] yes 
There’s http://en.wikipedia.org/wiki/Cruz_Bustamante\
From my experiences only, [name]Cruz[/name] appears to be a unisex name - more commonly feminine (or a part of [name]Maria[/name] de la [name]Cruz[/name] Surname) in Spain whereas it is more likely a masculine name in the Latin American regions. The Beckhams were definitely not the first to use it as a name, but they did bring it attention.
It is a very common surname and a less common feminine first name.
I think it is. I means [name]Cross[/name] but I have never heard it used as a girl’s name.