Here's what some of the airlines that operate in Spain charge for bikes. Might be useful to you if you'll be flying in this country:
Air Europa Gratis
British Airways Gratis
Lufthansa 40€
Ryanair 30€
SAS 30€
Spanair 30€
Vueling 30€
Iberia 150€
Bikes (except, perhaps, folders) are not allowed, unfortunately, on the high-speed AVE trains.
I was reading
on this blog about an American cyclist, Sue Knaup, who is a member of something called the Thunderhead Alliance. She comes to Europe every year to attend cycling conferences. When she gets to the country the conference will be held in, she buys a cheap bike, either new or second hand, and rides it around while she's over here. When she's ready to go back to the States, she looks for someone who looks like they could use a bike and gives it to them.
Some of the people who've received bikes from her have showered her with kisses and nearly been moved to tears.