Hi there! I don't live in Houston, but I've been there a few times. I live in Fort Worth, which is about 40 minutes west of Dallas. Houston is a 1 hour flight from DFW, but about a 3 and a half hour drive. So close depends on method of transportation.
Local attractions depends on what you are really interested in seeing. The Space Center is in Houston, which would be a neat experience, I'd imagine. I haven't been though.
There is the Kemah Boardwalk, which is a neat little place with restaurants, a few rides and shops. It's located south of Houston on the way to Galveston though.
Kemah Boardwalk
I must recommend going to Austin if you can and try the BBQ and Tex-Mex food. I'm sure some of the local Ledgies can steer you to some wonderful restaurants.
All cities have "rough" areas, but Houston overall is pretty safe. I went there a few years ago to see Lindsey by myself and was out at night downtown. Never felt unsafe. That's not to say you shouldn't be cautious because you should ALWAYS be aware and careful. If you can meet up with some other Ledgies, that is always a wonderful time and safety in numbers too!
Houston is a very heavy Spanish-speaking area, and there will be various billboards and signs in Spanish here and there (just like there are in certain areas of Fort Worth and Dallas). That said, I don't see you having any problems with things being in English. Although it has been a few years, so maybe the local Ledgies know more about this?
Crime statistics, I'm not sure of, but like I said, Houston is very safe overall. Now...if we are talking smog/air quality, that's a different story!

Houston is a HUGE city.
I hope your trip is long enough to visit some other cities such as Austin and San Antonio. I think you'll like those cities quite a bit. Perhaps Galveston or Corpus Christi as well.