As a confirmed fan of Imperial Spain, the answer to the question is: at war with everyone,all the time!
After fighting the French over Italy from 1494 to 1559 and the Protestants in Germany in the 1540s (not much naval action there), Spain had about 8 years' grace before the Dutch Revolt kicked off in 1567 (lots of naval action against the Dutch, all over the world). This lasted until 1648, during which Spain also found time to participate in the Thrity Years' War in Europe, followed by the Franco-Spanish War of 1648 to 1659. They were then at war again in Europe and the Americas another 5 times between 1688 and 1763. With a huge Empire in the Americas and the Caribbean,plus Portuguese possessions to defend after 1580, Spanish armies and navies weremore orless constantly at war with someone. Often fighting several different people at once. Strangely enough, although Spain lost most of its major wars after 1609, they didn't actually lose much territory.
So whatever period your Lego ships are meant to represent (in theory, anywhere between the 1550s and about 1780?), the Spanish can always be shoe-horned in somewhere. ShameLego have only ever done one truly Spanish imperial (armada) ship. I've currently got 10 Lego ships, with 63 minifigures....but only 4 Spaniards. Should be sufficient to fend off those troublesome Dutch, English, French and Swedish interlopers. Particularly once I've got the new Imperial Flagship....
