How do I request fellow car pooling members so that I am dropped at my destination first? Is 'Can I get down from the cab first?' correct?
The typical, in my experience (U.S.), usage is "drop off". Of your fellow passengers (from a multi-destination cab ride or carpool), as your comment indicates, you'd ask:
May I be dropped off first?
This is meaning 5 from oxford dictionaries
Set down or unload (a passenger or goods), especially on the way to somewhere else.
‘he dropped the load off at a dealer's’ ‘his mum dropped him outside and drove off to work’