Not huge on Mexican or seafood, but anything else works. BBQ and Italian would be my safe bets. Not really looking for a high end restaurant where you're expected to be in suit and tie, but at the same time I'm not looking to save a buck if the food is sketchy.
Here are a few recommendations I recently shared with a friend visiting NYC:
Dinosaur BBQ in Harlem. Worth the trek. Generous portions, friendly service, good brisket and ribs. The sides are great, especially the sweet potatoes with spicy peanuts and the collard greens.
Ippudo in Midtown West. The wait gets long, but the high end ramen here is awesome so try to go during off-peak times. Some of the newer ramen places in the East Village are supposed to be better, but this place is more conveniently located if you'll be in Times Square.
Pizza King in Midtown East. This is a good place to grab a slice or two while you walk around. It's not the best pizza around (in my opinion, that requires going to Queens or Brooklyn), but it's pretty legit NYC-style pizza. And the owner is very nice.
Thai Son in Chinatown. Cheap, authentic Vietnamese food. The place ain't pretty, but the food is delicious.
Jing Fong in Chinatown. Good dim sum, but avoid it on a Sunday since quality drops when it gets so busy.
Have fun, and feel free to PM me if you have any questions or want more suggestions.