The quickest way would be straight down the quays and out the port tunnel, now to be honest from experience, the taxi will take it's time this drives up the meter price plus at peak time as 6.30pm is you will have to pay the extra €10 toll for the tunnel, and will take about 40-50 mins, if I was u, Dublin bus have changed the 747/748 express route, it's €6 per adult €3 per under 16 under 3 are free, and it takes about the same time as a taxi, and leaves Huston every 15mins,