Restaurant near Hilton Hotel, Charlemount Place.

Keshk Cafe - Upper Leeson Street
Rigby's - Upper Leeson Street, just a few doors down from Keshk
Rotana - South Richmond Street, Portotbello
Seagrass - South Richmond Street, Portotbello, right beside Rotana

All of these of BYO, all are nice. Personally, I prefer Rotana and Keshk, both of which are Lebanese, North African fare.

For slightly less casual dining, Locks Brasserie, which is, in my opinion, one of the best places to eat in Dublin and without the fuss that comes with a michelin starred place.

All these places are 5 minutes walk from the Hilton.