Flighing to Barcelona and have 2 days before our cruise. What should we visit while where there. Thanks in advance.

Sagrada Familia, Gaudi (parc guell and his major houses/ buildings), las ramblas, dancing fountain, Cathedral...look on this website for destinations and then see what Fodors recommends as the 'don't miss sites" - alternatively, go to RickSteves.com and see his choices - cross reference the two. What time of year? What are your interests? there is a picasso museum, opera house to tour, shopping, marina, beachfront boardwalk,olympic village and venues etc.

Whatever interests you: http://www.fodors.com/world/europe/spain/barcelona

With only 2 days you'll need to do some research and choose what interests you. Book tickets before you arrive so you don't have to wait in line. This is only necessary for:

Sagrada Familia
La Pedrera
Casa Battlo
Opera House tour
Music performance at the Opera House

The other sights you can walk right in.

Cathedral
Parc Guell
Palau Guell

There's tons more to see and do in Barcelona but you haven't stated your interests.

Pretty much what others have said: all things Gaudi, Cathedral, Rambla, waterfront...

Add a stroll thru one of the big markets - la boqueria is off las ramblas

It is no longer possible to just walk into Parc Guell. Our daughter and I were in Barcelona last month on one of the remaining open entry days. Tickets are available online for €7 and limited to 400 per half hour to manage the choking crowds. There is also a ticket booth at the entrance to the park.

With any of the Gaudi sights, pre-purchasing your tickets is a time-saver. We had first-entry tickets for Sagrada Familia and found the basilica a beautiful place to visit before the tour buses began disgorging sightseers.

Whatever events are begin held or what takes your interest.
Neither of which you have kindly supplied. So in the absence of good information I can only suggest you look at the official tourism website.
http://www.barcelonaturisme.com/
I would also like to correct adrienne: You cannot just walk into Parc Guell any more.
http://www.parkguell.cat/en/

There are lines to get into Parc Guell? Even with the new E8 price?

Thanks to all. I was really asking for a friend and now she is going to become a member so she can ask her own questions.
Yes, I forgot to mention , mid September and where is a mid price place to stay...probably not too far from the cruise port, or where you think they could do some walking around and wine and dine.

If I go back to Barcelona I would stay in the Barri Gotic area, especially with only 2 days. There are tons of activities, restaurants, and people wandering around. I prefer some night life and sitting in a cafe or strolling around in the evening and looking at shops and people. And some place central to get to other sights. I stayed in a very quiet area of Eixample with limited restaurants and so we gravitated toward the Barri Gotic when we dined out and found ourselves in this area quite often.

With the limited time your friend should take taxis to get from place to place and not spend time on public transportation. I found it very easy to hail a cab and they were not that expensive for most of our trips.

Visited in August for 3 days and took day tour from Barcelona to Monserrat, was an amazing trip.....with special stop to Colonia/Gaudi's other incredible "unfinished" church, cute little town to, ... other days walked everywhere, Hotel 10 Mercado not far walk to beach..beautiful catheral across from hotel... eat or drink at "4Gats" where Picasso sat and "doodled" with all other famous artists...