Increasing the development from Algarve will not reduce the total monarch point costs of spreading the Renaissance there.
According to the wiki, this cost is rather constant (around 2000 monarch point), but for some institutions, it might increase the spreading rate so improve the timeline to get it.
I know... But in order to spread it faster (20 dev european province)...
Once Renaissance hits, my advice playing Portugal is at least give Lisbon and Porto to 20 dev.
That way you get the modifier to spread faster, in 1.18, Algarve was also a pretty solid choice to give 20 development, that way, Portugal could hit Renaissance faster, in 1.19, Algarve's development was dilluted due to the new province, personally, I think this is wrong, it makes Portugal get Renaissance way slower than Castille... Algarve, Beira, Coimbra, Porto and Lisboa are the most important regions of Portugal and they should get more dev/love than the other Iberian general provinces.
Coimbra: First portuguese university, made in 1290! Also land where D. Dinis ordered to plant several thousands of trees to make ships in the future and to prevent the sea from turning Portugal into desert...
Algarve: Land of discovery, where Portugal planted sugar, some tropical fruits and where started the whole thing of discovery age... And the estuary of Guadiana River is in the border between Algarve and Sevilla, not Sevilla, ffs!
Beira: Land of the order of Christ, after pope banish the templars, all of them were exiled to the city of Tomar, they were one of most richest institutions in Europe and provided highly disciplined troops and skilled explorers (even monarchs) to Portugal.
Porto: Heck, everyone knows Porto, one of the best wines in the world and a 100k city in 1500... Also has a beautiful river
Lisbon: The capital, this estuary made the greatest ships of the shining days of Portugal... 200K ppl in 1500... Even in the Personal Union under Philip II, the capital of the Spanish Empire was changed to Lisbon... in 1582!