Yes - it's posible to download the game for free / prior purchase but

A) There is no free weekend (has been posponed)
B) While the core part of the game and launcher can be downloaded free, yu need to have the active account to login into game to download the "rest" of the game (patches) so your sub will be running anyway.

Any chance you can take your PC or PS3/4 to some friend to have it downloaded faster there?