I'd love some restaurant recommendations for Barcelona in May. It's easy to find lists of very high-end restaurants, so I'm more interested in learning about mid-range to cheap-eats places where we can grab a quick lunch or have a nice sit-down dinner. I know mid-range can be relative, so I'm thinking entrees between 20-50 euros. Wine/alcohol is not of interest; seafood is of moderate interest (I don't eat it but my traveling companion does). We're interested in a variety of cuisines.

These are for more for grabbing a great tapas-centric lunch rather than a casual sit-down dinner, other than Paco Meralgo & Llamber below:

In the Eixample,
for very casual and a wide variety of tapas and long hours, Cerveseria Catalana and its sister restaurant, Ciutat Comtal
For very creative small plates, amusing waiters and a bit higher end, Paco Meralgo and Tapas 24 (go here at an off hour because it's always crowded)

In the Ciutat Vella (Old City)
Tapeo
Llamber (perfect for a sit-down dinner, moderately priced, cuisine from Asturias)

In Barceloneta
La Cova Fumada, an institution famous for its bombas

Tlaxcal, in The Born.

Thank you Maribel and HeHateTweeter, I'll check those out!

We had a lovely dinner at Teoric Taverna in September, which was within walking distance of our hotel in the Eixample. They have two seatings at dinner and a set menu. I believe was about 40 euros per person, food only. The food and wine were delicious, and the service was friendly.

Ditto to Teoric, which I forgot!