There are two factors that I like to keep in mind when discussing post-adolescent Spaniard behavior:
1) Spanish couples date an inordinately long time. It's not uncommon for a couple to "go together" for 8-10 years before tying the knot. Although I haven't asked anyone specifically, I'd wager to say that the premarital relations are somewhat commonplace.
2) Most post-adolescents who are not away at college still live with their families. Therefore, for many, the only place to be intimate is in a club, on a metro or, more commonly, in the park...where the "spider" is as common as the dirt paths leading to the benches. [If you don't know what the "spider" is, you've never been to the Retiro in the afternoon.]
This accounts for a couple of interesting phenomenae: Getting married and getting started on families much later than other cultures, and closer family ties.
How does this relate to you, you ask? I think you'll do your best to frequent public places with a friend [same gender] and just be brave. I've found that the novelty of "not being from around here" works well to break the ice. Whether you have a personality and something intelligent to say is up to you...and will determine how well you may get to know someone. Spaniards [in my experience, the women] seem "open" enough to carry on what you may consider a normal dating relationship.
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Ongi etorri!