Er, IAH to downtown can either be Taxi if you don't care about price and if you do, then super shuttle which is just a shared ride bus. Taxis aren't as prevalent as say LA, driving around Houston isn't bad either if you did want to rent a car. As far as where to be, you'll either be on Montrose/Westheimer area, also downtown there are some new bars/resturauants, but it's pretty quiet outside of work days. You'll want to check out the places around Market Sqaure park.