I used to visit a place just on the Spanish side from the Alrgarve for work all year round. Late Oct could be very pleasant indeed, with mid 20s and warm seas. It was a popular time for locals to take a break. However – it could also be pretty cold and windy (it’s a very windy place), with relatively short daylight hours. It does also rain, hence the greenery.
Tbh it depends on what you want to do. If it’s beach and lounging by the pool, it would be a risky time of year. If you want to a mixture of stuff including sporty or sight seeing days where heat would be an issue it could ideal.
If it were me, I might look more over Andalucia on the Spanish side where you can combine all sorts of sports, beaches, fantastic cities and touristic sites giving you options whatever the weather.