If  your thing is interacting with locals than you have to visit Lisbon in June.

The Lisboetas (the inhabitants of Lisbon) like parties, traditions and sardines and what better time is there to take advantage of all this than in June? Because June is the month of the festas dos Santos Populares (Feast Days of the Popular Saints). In the evening of 12th June, pots of basil, colourful paper carnations and casks of wine are everywhere. There’s a definite whiff of grilled sardines on street corners and Lisbon becomes one big street party.

There are parades in each district and everywhere there is music and dancing. In the evening, make your way up to the Alfama, where sardines are grilled outside the houses and the narrow streets fill with people in a party mood.

There is a big parade on the night of the 12 June for St Antonio which makes its way along the Avenida da Liberdade. The old quarters of Alfama and Mouraria are particularly busy and celebrations continue until dawn
On St Peter's Day there's a boat procession on the Tagus (the river which runs through Lisbon) near Montijo, which is situated on the opposite side of the river from the capital, dating back to the Middle Ages.