You wont need taxi counter, just walk out the door after customs to the taxi stand, look for Vinasun or Mai Linh taxi only, both are very good.
Taxi to District 1 in August for us was about 140,000-150,000 dong ($7-8 USD).

Wife and i only ever use Vinasun and never ever had a problem with them, good drivers, clean and good aircon.^