We just noticed that the Festival of Santo Antonio is on June 12-13 and that we could plan our trip around going there if we wanted. We’re wondering how crowded it would be. Do hotels book up months in advance? Would the festival make it difficult to do other sightseeing on those days; for example, would tourist attractions be closed? Also, if we are in Lisbon on Portuguese National Day, would tourist attractions be closed then as well?
The biggest celebration on June 12-13 is in Alfama. That area of town will definitely be more crowded and I would suggest not staying in that area during that time - unless you have no need for sleep!
Lisbon has become a very busy place all summer so book hotels or apartments well in advance. The other areas of town should have business as usual during that time.
I was in Lisbon on Portugal National Day two years ago and didn't even know it was a holiday. Banks and post office will be closed, but in the tourist areas, you won't even notice it's a holiday.
The Festas do Santo Antonio includes parades, celebrations, and street parties throughout the historic center of Lisbon. It is a great street party that is very local. Social clubs, church groups, and neighborhood associations will set up food and drink booths in the Alfama, Graca, Bica, and nearby neighborhoods, and the party will go on all night. You can check out videos on You Tube.
The more modern neighborhoods may have some street events, but much less intense. To my knowledge, these celebrations are limited to central Lisbon, so if you wanted to avoid them, you could stay in one of the many communities to the west of downtown.