I had dinner at Amaltea with my girlfriend last Friday. There is a special menu for vegetarians/vegans, and it's a full menu with a lot of options.
We shared the hummus and it was delicious, then we got a main dish each and both were good. The wine selection is also impressive.
I think that you don't get much better than this as a vegetarian-friendly restaurant. Actually, before going there we had a look at the menu of La Boca and found that there were only a few dishes that were vegetarian or could be made vegetarian, that is why we decided for the Amaltea.
Cons: A bit more pricey than the average