Most of the cab drivers I have had tend to be from foreign but not from a country with Spanish as a first language. I haven't had any issues on be able to speak to the drivers. If your worried about it get a smart phone app like "sayhi" that can translate for you. Cab should cost about 60-70 bucks from IAH to downtown. Yellow cab is the main cab company and they have a good app if you use a smart phone. Supershuttle is per person, I think last time i took was 20 or 25 bucks and not worth it. You could be the last drop off and have to everyone elses drop off before they go downtown.

In the downtown area I don't feel there is a lot to do. Only things I can think of are the aquarium which will probably be in most top ten lists, sporting events, or discovery green. Discovery green is an area just outside your hotel that has a nice pond and is park that is neat area to just relax at.

You are located well centrally and a slight walk to the metro rail. With the metro rail you can get to the museum districts and see a lot more things. Google metro rail houston and you can find more info about the rail, I don't use it so I can't really tell you much about it. Its mainly set up for commuters not tourists.