IAH is north of downtown and depending on time of day it can be a long haul. The line you refer to must be a bus line as the light rail only goes around downtown not to the airport (or where people live and want to go for that matter. Airports, Katy area, Galveston etc). There are some bestbuys on 59 and 45 near the airport. Might want to look into renting a car fir the day if you run around as taxi prices will eat you up and probably come out ahead with a car.