There is never a bad time to knit (well, except church services and parent/teacher conferences... there have been many discussions among knitters on this topic)!
But there really is no other hobby that seems quite so productive (yes handheld video games are portable, but you can't wear them when you complete a level), that can go quite so many places. I learned to knit because I had a long train commute to work -- it was perfect! Once I learned to knit, I simply chose projects that required only one ball of yarn at a time and used short needles to avoid poking the commuter next to me. Many knitters keep a sock project on hand especially for waiting in line at the post office (not much is smaller than a sock project). I keep one in my car so that when construction brings traffic to a halt, everyone around me is cursing in their cars while I calmly knit away on my current project.
Not only is it portable, but knitting is also a form of meditation. Choosing a simple, repetitive pattern can be like repeating a soothing mantra, while choosing something more complicated can refocus all your attention on the task at hand and force your mind to release whatever has been causing it to jump around through hoops.
Knitting offers a wide range of flexibility as well. If you like a challenge, there are many many stitches, techniques, and pattern types that you can try out. If you like to be productive and don't feel like struggling, there are plenty of beautiful items that can be knit using only the most basic knit/purl stitches.
Best of all, I find that knitters (and crocheters; I do both and am not prejudiced against either one!) are some of the nicest people in the world! I had a stranger on the train offer to help me when I was struggling to make an i-cord for the first time, and never until I knit was I able to walk into a group of people and instantly join the conversation. Knitters love to share... share yarn, stories, projects, successes.... you know you've found a knitter when someone comes up to you and touches your hand-knit scarf and comments on the fiber, or colors, or incredible workmanship.
Now that I knit, I find it difficult to comprehend someone not wanting to knit! :) Once you learn (lucky you--- I have a beginner's class starting on March 12th that you could take!), you have an ultimately-portable, productive, and varied hobby. There is always something new to learn, and there are dozens upon dozens of books, magazines, web sites, and yarn stores with patterns and resources and smiling faces ready to help you with your next project.