How quickly can someone learn to fly?
I did it in 17 days - start to finish.

Did flight school in Arizona.  Before I went, I got the PPL study guide, MS Flight Simulator complete with a yoke, pedals, and throttle quadrant... and put in dozens of hours just learning the instrument scan and practicing virtual stuff.  

When I got to the flight school, I already knew the parts of the plane, and what each control did.  I knew about maps and plotting courses.  I understood the physics of flight.  I knew about VORs, VASIs, NDBs... I knew about stalls and corrective procedures - from an academic standpoint.

As such, my under-the-hood training was by-the-numbers.  My seat of the pants stuff was only hampered the first few days by the awful flying conditions of AZ in July heat.  

That said, I aced the written, and did my 3 required solos in two days.  I went to a flight school run by a Gold Seal licensed FAA examiner so I didn't have to depend on the FAA to squeeze me in.  And I passed.  17 days.  

ONLY flew tricycle gear stuff.  No taildraggers.

Other than the serious prep beforehand, there were three main drivers for my success:


I flew at LEAST once a day - many times twice.
I wanted this more than anything I had ever wanted before.  
I only had enough money and vacation accrued to be there for 3 weeks total - no more.  


Best of luck!