sgerene, they will ask for your passport at the hostels when you check in to take down your info.
Can't help ya with those unpaid parking tickets (my dad is a cop but his jurisdiction ends in the town on Long Island that he works in

) but I will tell you that it is VERY rare to see someone get carded at a club or bar here in Spain due to the fact that even the near "kiddies" can drink.
If you look like you are 8 they may ask for ID but I doubt it.
As I said above, you will need some substantial ID if you pay for things with credit cards. If you are really not wanting to bring your driver's license, you could use your passport as ID everywhere you may need it but that would require you to bring it out at night too. Get yourself a good under the pants waist wallet and you should be ok.
Unless you have like 1,000,000 unpaid parking tickets I still think that losing your driver's license is better than losing your passport
Anyone else have experience with this?
Saludos,
jer...