I think it means, either he thought he knew you, he was flashing his lights to the tune of the music on his stereo or he'd got his sleeve caught on the light stick!!!!!! ... or he could have been an expat???

Seriously tho, I've no idea! In the UK its supposed to mean warning, but people nearly always use it as a "go on then"

Spanish driving is a complete mystery to me!! I wouldnt even hazzard a guess at what the horn means in Spain, half the time its cos they've seen their mate and they follow it by doing an emergency stop and hanging out of their window to have a chat!

Jo xx