I've decided to use pyechonest's Track.track.tempo & .key
This method does not output and print saying that the music file is being uploaded (I guess to echonest's server), but I believe it is (still takes ~2 minutes), and that it is still doing analysis for all track.track's attributes (analysis_channels, energy, loudness, etc) even though I only want tempo & key.
I believe I could reduce the time significantly if I simply use the tempo & key attributes in track.track
P.S. You guys provide an awesome service! Thank you!