I don't know how strong your back is, but "cafe" style bikes aren't the most comfortable to ride. For commuting, a bike that has you sitting straight up is going to be most comfortable. There are so many factors that will dictate the best bike for your needs.
Start with:
--What kind of riding do you want to do?
--What is your weight/dimensions?
--What is your price range?
--What do you want to get out of your motorcycle?
And then research the best used motorcycle within your range. I say "used" because there isn't much sense to going out and buying a shiny new bike that you're just going to lay down and bash up. Try and stick with reputable Japanese models that have had long production runs. Avoid big, fast bikes, as you'll be entering the game out of your league. Talk to people who ride, find out their opinions and then take those opinions with a huge grain of salt. Motorcycle salesmen especially...they're like car salesmen, but they deal with overcompensating midlife crisis sufferers, adrenaline junkies and wannabe racers all day, and it has often muddled their focus.
Don't rush into anything. Take your time, find the bike that's best for you, most importantly go and BUY ALL THE BEST FxxxING SAFETY GEAR YOU CAN, AND THEN WEAR IT EVERY TIME YOU RIDE!!!! You're gonna need them. Helmet, jacket, boots, gloves, and splurge on a nice neck brace. Yes, you'll look kind of ridiculous, but you'll look ridiculous on your feet.