find a decent road bike! get a fixed gear one (one with only one gear) you can easily make any road bike a fixed gear.
AS ridiculous as this sounds. use this bike to get everywhere! Keep your
HIIT however a fixed gear allows you to adapt to using one gear whether you are biking incline (up a hill) or decline (down a hill). Make it stick to a harder gear, this will give you great results i'm serious! I burned off 10 lbs using a road bike before I got in to weight training.
If you can master cycling on a hard fixed gear it'll do great things to the strength of your legs and your weight loss goals!
Sure, you could do the same thing to a treadmill or elliptical machine but thats you in a stationary place staring at a clock. Cycling will take your mind of a clock and give you the mind-set of destination, different ways to get there and the challenge of getting there as fast as you can!