The surname DULDULAO is of native Filipino origin, and according to this website:
http://store.escalate.com/store/turoturo/article7.jsp it means in the Tagalog language: "to thrust".
This website:
http://www.bibingka.com/names/default.htm will give you some background history on native Filipino names and the Spanish.
This website:
http://genforum.genealogy.com/php/search.php?forum=philippines&url=%2Fphilippines%2F&path=%2Fphilippines%2F&terms=duldulao&boolean=AND is where you can read about other Duldulaos inquiring about their family history, and where you can also post your own inquiries.
-- Nanaea