Parc Guell is ok, but horribly overrun by yoots.
Fundació Juan Miro is excellent.
In contrast, we went about 6 months ago and really liked Parc Guell. Had a lovely wander round and then ate lunch on the benches at the top looking out over the city.
And we didn’t think the Miro place wasn’t worth it. The only good thing was the mercury fountain. MACBA was better if you like modern art, but I think you’ve got to really be ‘into’ modern art to like either of them. If you can look at the singed frame of a canvas that’s been set on fire and think “wow, that’s incredible” then the Miro place is for you, if not, give it a miss.
La Pedrera is worth a trip, as is Sagrada Familia. Basiaclly, if Gaudi touched it then it’s good.
We were there for a week so had plenty of time to wander round, so for us the walk up to Montjuic was a nice way to spend a couple of hours. But you can get a bus up there if you wanted to speed it along.
For food, head towards Placa Del Pi and just find somewhere in the little side streets. Although we ended up at a fantastic Italian called Via dei Mille near the junction of Carrer d’arago and Passeig de Sant Joan. The house wine was Amerone, we drank a bottle of it for about €10, and had a stunning pizza for about €8 each. No other English people in there, just Spanish and Italians as it’s away from the main touristy area.