In Ireland most restaurants offer ealy-bird specials - a full menu early in the evening (usually 5pm - 7pm) which is great value. There are lots of decent restaurants a short walk from Grafton St, many will have a vegetarian and even vegan option. Coppinger Row Sophie's Restaurant, Bar & Terrace
Etto on Merrion Row, if you like Thai, Saba is good, Wagamama on Sth.King St. is a good, casual Japanese. Dunne and Crescenzi
is a decent, casual Italian. A little more upmarket but with a great early-bird special is Pichet
(a 10 minute walk) or, one of my favourite little places The Vintage Kitchen
(exceptional value for lunch and a byo wine) - book ahead it's always busy and is a tiny place but the food is consistently good.