Sao Joao´s celebration (Porto)

Hello international community! I am a spanish girl living in Lisbon and this week end I am going to stay in Porto for the Sao Joao´s celebration.
There is any local community meeting or somebody is available to enjoy together this big party?

As I will be there on my own, I will be grateful too for some advice on where to go in the evening,

Thanks in advance,
Amaya