Hello Renan!

We all would like to help you but you didn't gave very much information about your father.
First of all are you sure he is living in Spain at this moment? He could probably live in any other country, even in the vast U.S.A.
When was the last time your mother saw him or had news from him. Where he was then?

Fortunately Escalera is a very unsual surname but remember that all Spanish people have two surnames, the first one is from our father and the second one from our mother. Giving us the second surname could help.
Your father's age and birthplace could very useful too.
The white and yellow pages could be useful only if your father had a telephone line of his own in Spain.
There 43 milion people in Spain and not all of the them are internet users, furthermmore only a few of us are MadridMan web page members (a few hundreds perhaps. What do you think MM? I think is less than that).

I searched on Google for "Mauricio Escalera" and I found two people in México with that name.

Good luck