My favorite carts in Midtown are the XPL chicken/lamb and rice guys on the southwest corner of 48th and Park and the NYC Cravings truck (no consistent location that I've been able to discern) for Taiwanese fried chicken.
If you're interested, Midtownlunch.com is the Bible for questions about Midtown street food.
http://midtownlunch.com/2009/05/12/n...le-food-scene/