Barcelona are so close to making their league title official now. Espanyol is their next opponent and winning against them will guarantee their championship this season. Espanyol might cause some trouble maybe because of trying to get out of the relegation zone. But I don't think it would be a big deal for Barcelona as long as they play their usual game for the declaration of their championship.
The only fun thing to watch in the La Liga is the competition between Real Madrid and Atletico Madrid for the 2nd position now. Real Madrid don't seem to be very dedicated about it though.
One never knows what to expect from a "derbi", and you just mentioned two. About the Catalonian derbi, although this match is really important for Espanyol I don't think Barça will relax their game because mathematical victory gives a lot of peace of mind; but who knows, Espanyol could try to do their best and eventually get a point from a draw.
On the other hand, a Madrileñan derbi is always exciting, but this season the second leg is so important in order to end 2nd or 3rd in the standings that it will be even more, if possible.
But this is not the only fun thing remaining in La Liga: qualifications for different European competitions next year are still at stake and temas in positions from 5th to 9th won't give up in their efforts to access until the last moment.