Prego's good, but expensive. Great pizza and calamari, which we lived on while our kitchen was torn out. It's on University. There's a D'amico's deli on morningside that serves very traditional Italian that's cheaper than Prego and very good.
Our daughter's favorites are Indian food at Shiva on Times or Cuban food at El Meson on University, both of those get lots of neighborhood traffic and are less stuffy than Prego. There's a very good, very small Vietnamese place, Miss Saigon Cafe, off Times. Our favorite is pretty pricey, but stellar and a neighborhood favorite, Cafe Rabelais on Times. Pretty casual, no reservations, get there at 6:15 or 8. It's the best traditional French in houston. They don't do veal kidneys cooked in their own fat or anything, but come to think of it that's just as well.
Have a great visit. If you go by Martel tell my daughter hello.
Mark's really isn't the Rice neighborhood, and I've only been there a couple of times, but it just never clicked with me. Hugo's is near there and it's pretty fun: it's interior Mexican mostly. Also Cafe Montrose on Westheimer has good Belgian food and great Belgian beer.