Totally convenient from Link at the Westlake stop. A block and a half from the entrances/exits near Macy’s and McDonald’s.

Personally, I would take Link and use a rideshare (Lyft/Uber) carshare (Zipcar/Car2go/ReachNow) service because you won’t have to mess around with parking. There are some traditional rental places in downtown as well: Hertz, Avis, Enterprise/Alamo/National within a few blocks. Hertz sometimes is cheaper downtown than at the airport.