Don't go here. Go to Sovana Bistro instead - its lovely. On to the review:
Portobello does not have a gluten free menu. You order off the regular menu and have to ask the waiter the usual questions about the dishes. In my case, the waiter was extremely disinterested in helping me and instead focused on the other tables. Any question I managed to eke out was answered in a simplified and hasty manner before he hurriedly left. I was not told they have gf bread; instead 1 roll was brought to the table halfway thru my meal. Also I've read that if you are ordering gf, the chef personally comes to your table; this too did not happen. Please note I was there in off-season, during the week - so there really is no excuse for them.