Translation:Do you have a taxi?
I'm not sure, but since the location is not mentioned here, this sentence means "Do you have a taxi?". For example, replace 택시가 with 펜이 and the meaning would be much more clear.
Is there a taxi - 택시가 거기(에) 있느냐? I think.
Or is it possible to omit location in Korean sentence with 있다?