Porto and Lisbon?

Have ticket for Optimus Primavera Sound in Porto on 31st May.
Line-up isn't great, so I only got the Friday day-ticket.
What do you recommend to see and do in Porto on Saturday/Sunday?

Haven't been to Portugal before, so would like to see a bit.

I'm also thinking of going to Lisbon, if it's worth it, or is there somewhere else I should see?

I can tag on a few days before or after Porto - what do you suggest?

Budget to mid-range.

Why not? Lisbon is a really nice city...much to do there than in Porto IMHO.

Depends on your interests of course...what do you like doing? I spent most of my time in Porto eating and drinking..visiting port distilleries,small bars and cafes...

Porto has a lot to see and to do and I bet it'll be even more prosperous at that time of the event.
If you want some traditional sightseeing - which BTW is really worth doing - you can visit the historical city centre and Gaia - the other side of the river - and visit (and try) the Port wine cellars. You can do that on foot or bike and there's organised group walks.
On the other hand Porto has the best Contemporary Art museum in Portugal - http://www.serralves.pt/pt/ - and Casa da Music - Music Hall made by the finest architects.
There's a new design around Rua Miguel Bombarda and Clérigos district that bursts with nice people and places (cafes, galleries, shops) just to hang out and visit.
So there you have, both traditiona and contemporary options for your short stay. If you're staying downtown anyone can point it out for you.

But as said before it all depends on your interests. I lived for 15 years in Porto and it's getting better and Lisboa will always be charming and beautiful and with lots to see - also historical and contemporary - and more options just because it's bigger and central. Definitely worth coming for 2/3 days.

Feel free to ask more about both or other places and have a great time here in Portugal!

Thanks both

Will definitely explore the old city- very much enjoy getting lost in the warrens in old quarters of cities!
People watching from little cafes is always enjoyable of course.

Due to other restrictions, I'll now only be 24 hours in Lisbon before I leave portugal.

Any specific tips?

Also, any budget-friendly recommendations on places to stay very welcome!

To eat cheap n' good for lunch, ask the "prato do dia" inside small restaurant.. this is always something very tasty and complet (like a soup pork and rice + coffe glass of wine), usualy between 5€ and 8€..

In Lisbon, at night you can go to the Bairro Alto, there are many bars and music..