While is is very common for SIMs to be mailed for free within the country, I've never seen any provider mail out of country.
If it is important enough to you to have your SIM before arrival, there are many Spanish SIMS for sale on ebay. It appears from a quick look that many of the sellers claim they can pre-activate the SIM for you with your passport number, which might tip the balance towards the ebay option.
Originally Posted by
cheltzel
Answering my own question ... I went through the purchase menus enough to see that you need a local address for delivery.