Day trips while in Barcelona, possibly France?

I haven't been to that part of France yet, so I can't comment on the specific destinations you mentioned. What I would suggest, though, is that you make your day-trip(s) to places a bit closer to Barcelona so you spend less time on the train/bus and more time actually walking around. Catalunya has a lot to offer. If you scan back through the Spain forum, you'll see many posts asking about things to do in that area.

Since Barcelona is a big city, you might want to get some variety into your trip by visiting Montserrat (good for walks, and probably a bit cooler than Barcelona), the lovely small city of Girona (less than an hour by train), Figueres if you're interested in the Dali Theatre and Museum, or one of the beach towns. If Roman antiquities interest you, Tarragona would be good.

I also haven't visited Valencia, so no help there, either. Madrid has much to recommend it, but unless you feel you can't visit Spain without seeing the Prado, I wouldn't make a day-trip to Madrid. It's a city that, aside from its own sights, is a great base for day-trips to some fabulous nearby destinations. You wouldn't have time for those on a day-trip. Save Madrid and its environs for your next trip to Spain.

Thank you acraven, I think that is exactly what I needed to hear! Just stick in the area, soak in my surroundings, and not to stress about trying to go to farther and do more!

Agree, don't go trouping too far afield. Monserrat is a wild, unforgettable place--practically a whole city perched on the serrated mountain top. It's busy, with many day trippers from Barcelona who I think come by bus. (We had a car. Absolutely do not recommend driving up the mountain unless you have serious experience with hairpin turns.) But the crowds were managed well and it's cool to see a pilgramage site being, well, the focus of pilgramages. We took the funicular that goes up the mountain from the church level and walked back down to the church... maybe it took an hour or so, and that got us away from the crowds. Took a picnic to eat on the way down.

I second the idea of Montserrat. I did this in 2010 when staying over a couple of days in Barcelona after a business trip and enjoyed it. The setting is spectacular, there is good hiking, and the art museum is very nice. I was going to say Collioure which is just over the border with France but at three hours each way it's too far. Madrid is about the same, looks like the fastest train still takes 2:45. As much as I love Madrid that's too much for a day trip. The bahn.de site is good to get an idea of what train journeys are possible. I usually rely on that when just testing out ideas but the Spanish rail site probably works well too.

I took a train from Valencia to BCN last year. It's about a 3 hour train ride. It's pretty because you get to see parts of the sea along the way, but Valencia was an ok city to visit. It certainly has it's charm, but not like BCN. If the train ride were shorter, I would say check it out.