Try Azuma (sushi) on Main its attached to the building that houses the Rice Lofts.
Zeros is a small sandwich shop but its great!
I feel like downtown Houston is small but you may want to cab it to where Cabo is - good Tex-Mex or take the hotel shuttle to the original Ninfa's off Navigation Rd. (they invented fatijas)
A great beer menu - try Flying Saucer 100+ beers great atmosphere.
Sake' Lounge in Bayou City Place is in walking distance. I think they are better for sushi than Azuma, and I believe it's closer. It's a straight walk down Louisiana.
There are lots of places springing up on Main as well.
Don't forget that the Hyatt's concierge can also give recommendations and can find out which places are open when you want to go.