For my money it's Cafe Ba Ba Reeba. Normally I'm not into corporate restos but they do a good job here. Good selection of tapas and great sangria. If it's nice outside, choose a table on the patio and people watch.
We have been to Firefly, Cafe Ba Ba Reeba, RE Tapas and Cafe Deia. We enjoyed all of our meals, but Cafe Deia was the best. You can purchase discounted gift certificates to all but the Firefly on restaurant.com.