Unfortunately there is no subway service from 8th St to La Guardia airport. I have found that the best and fastest way is to take the A train to 125th st. From there you can catch the M60 bus going towards Queens (free transfer), which will take you to all terminals at LGA.
Great question Vicki Dawson. I do believe there is a express Bus. There is a lot of service changes due to MTA FastTrack program. Can you check the MTA website to be sure before heading out?
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