We ate there in 2004 and enjoyed the meal.
We just haven’t been back since because I really really like Fulton’s.
As everyone else points out, Portobello isn’t part of the regular or deluxe dining plan.
Back in 2004 they did participate in the dining plans that were part of the silver, gold, and platinum (grand) plan packages.
If you are interested in spending money for one of the current all inclusive vacation plans, both Portobello and Fulton’s participate in them. But of course, these are premium plans that also include unlimited recreation, (most) tours, and deluxe plus dining (several restaurants that don’t do the more popular plans participate), and La Nouba tickets.