If you've been to Florida or California's beautiful beaches then Galveston will feel lame in comparison. The town is small but has its charm, especially during the day when you can see the beautiful southern architecture. The $10 ticket to see the Ocean Star oil rig in Galveston is well worth it if you have any interest in science/engineering or want to see something cool. There are a couple nice hotels along the main beach, they are just a few minutes drive to the little downtown.
Houston is roughly 70 minutes from Galveston. Discovery Park area in downtown is neat but I walked the rest of downtown and there's really not much to do. Unlike other downtowns there's no central shopping district, you have to drive a little west to the Galleria which is pretty nice. There's some beautiful homes out there too. I can't comment on Houston's nightlife and dining since I was staying in Galveston. Houston is very visibly diverse, so I'm sure the dining scene is great.
Buffalo Bayou is not one of the beautiful waterfronts you see in other cities but is still worth checking out for a little bit. Rice Village is worth a visit for Torchy's Taco's, if you've been to Seattle it's like University Village but much smaller.
Honestly, Houston was the only American city I ran out of stuff to do, but I will surely return one day for the Johnson Space Center. The entire metropolis is too spread out and suburban.
