MX5, without question.
Reliable, good looking, cheap to buy, cheap to run. Handles very well and goes reasonably fast. Best gear shift of any car outside of a Ferrari open gate. Dog can sit on the rear shelf.
Don't know about availability in Spain but have you considered a Toyota MR2 Roadster?
I've had mine for over 2 years now and it's been excellent fun and incredibly cheap to run.
Pro's:
Mid engined
Rear wheel drive
Bullet proof engine (avoid earlier examples) and mechanicals
Very good mpg
Low centre of gravity
Very light (lighter than an MX5)
Bigger interior than the MX5 (I'm 6' 4" and can fit comfortably)
Cheap to buy (in the UK at least)
Cheap insurance
The lack of weight means tyres, brake pads etc last a long, long time and I can get over 45mpg if I don't thrash it too much.
Con's
Not a lot of stowage space. A frunk up front and storage behind the seats and that's it really.
My wife summed ours up nicely when she said that even boring journey's seem like a summers holiday.
Cheers,
Gary