Best way to Allstate Arena from downtown Chicago?

What is the best (fastest) way, other than a taxi...to get from downtown (MI Ave area) to the Allstate Arena? I say the trip planner on the cta website, but someone also said that I should look into the metra rail? Any suggestions? We're going to a concert next month, but staying downtown at the Ambassador East Hotel.|||I would greatly suggest Metra or Blue Line both will take you into Rosemont, but then you will to take a taxi.|||I'd take the blue line