Porto isn't a suitable GA field - handling about 400 euros, and no club/hire operations as far as I'm aware.
There is a GA field to the south of Porto which may be more suitable.
The Algarve area has more opportunities. There's even a Chippy available at Portimao, G- reg.d I believe.
Private flying is a bit sparse in Portugal, so you may need to search around.
Thanks, this is what I'm starting to find. Perhaps I am just going to bite the bullet and hire a car instead. Given I'm right oop norf of Portgual, I'll probably head to Spain. Shame I'm a shameless airfield log book collector.