I need a plan for Montjuïc

If you are not interested in the museums (nothing wrong with that), then what does interest you at Montjuic? That will determine how you get there and spend your time.

I took the metro to the funicular to the cable car; only the cable car has views, and it lets you off near the castle. I then walked downhill a bit passing several museums, before getting on the bus to go the rest of the way down. I spent several hours at the MNAC (it's huge and not crowded), then saw the CaixaForum (for the Modernista roof), then walked past the fountains to Las Arenas (a former bullring converted into a shopping mall). The view from the roof of Las Arenas is fun; you can take the escalators inside the mall to the roof for free, or take an elevator outside the mall to the roof for a small fee.

If you are mainly interested in the fountains, you can take the metro to Placa de Espanya, then walk and take escalators up to them.

Is this your first visit to Barcelona; if not, getting there is half the fun (so to speak). On a previous visit, we went to Barceloneta and took the aerial gondola from St. Sebastia (regrettably, there will probably be a long queue) up to Montjuic. From there we took the bus to Fundacio Joan Miro (but, alas, it was closed). Near the Joan Miro, you can take the Teleferic de Montjuic to the Castle. You could walk down from the Castle to the Joan Miro, or take the bus on down to the Palau Nacional d'Art de Catalunya. You may want to disembark there and walk down to the fountain. If you're interested in architecture, stop and visit the Mies van der Rohe Pavillion. The suggestion about Las Arenas is a good one. The Arenas is shopping center, yes, but the rooftop view is quite nice. We had dinner at one of the restaurants at the roof at sundown.

Thank you! Yes, this is our first time in Barcelona. We would have spent most of the day at Montserrat on this day so probably it sounds like we would see the castle, walk down and see things on the way, maybe take the bus to Las Arenas (I assume that we can eat dinner or a snack there) and see the fountains. Or depending on what time we get there and the castle is closed, maybe just see the fountains.

I guess the real question is: is Montjuïc worth going to for us? This would be day 4 in Barcelona, a Friday. We would have already seen Sagrada Familia, Park Guell, Montserrat, Barri Gothic, El Born, Garcia, Las Ramblas/La Boqueria, a tour at Casa Batllo and concert, a concert at Palau de la Musica Catalana, Bascilica de la Santa Maria. We could also swap out Montjuïc for Playa de Bogatell or go to Festa Major de Sants. The last day, a Saturday morning before taking the 3:30 train to San Sebastian, we will go Mercat de Santa Canterina, Catedral and Picasso Museum.

I love museums but my 16 year old daughter can only take so much.

You have a packed schedule. I wouldn't lock in Montjuic until you see how you feel. Once you get to Barcelona, you may be more interested in other things, or you may learn of a special event that sounds enticing. I went to Montjuic for the Miro Museum and MNAC and took different paths up and down on those two occasions. Otherwise, I didn't have a burning desire to see things on the hill, so I used my time (10 days) for more museums and a lot of modernista sites. I know I would have enjoyed the fountain, but that was too late at night for me.

I'd seriously consider the festa, but I haven't attended it myself so I can't provide a personal recommendation..

Try this plan of attack ... easy on your time, and easy on your feet.
1. Metro to Parallel
2. Funicular to ‘Parc de Montjuic’
3. Teleferic (return) to ‘Castelo’
4. Walk to Joan Miro Foundation ( I highly recommend a visit)
5. Walk past Olympic Ring stadiums and tower
6. Walk by the Palau Nacional (MNAC) and down escalators to Placa Espanya
7. Visit Las Arenas
8. Stay on for Magic Fountains show (if playing)

Yes, I think we'll play it by ear and see how we feel after all day in Montserrat.

David, thanks for the plan of attack! I will put that in my notes :)

I just googled my hotel and we are a 3 min walk to the red line metro and it's a straight 11 min metro ride to Plaça Espanya to the magic fountains. So if nothing else, if we feel up to to it, that might be a nice thing to do our last night.

We took a taxi from Las ramblas, walked the fort, visited the modern art museum and walked DOWN into the city. That was our final 1/2 day before catching train to Madrid about 2 PM. Taxis are quite reasonable and save a lot of time in a short day.