Hi,
I was on L1 visa last year and moved to H1B in Oct and moved to another state. My wife(L2 with SSN)and kid(US Citizen) left for India in January 2011 last week. Whole year they were in India expect Jan(~11 months.).

Can I file tax return jointly? Or I need to file as single and no dependent.

Yes, you can file jointly. Your wife could be on Mars for all the IRS cares.

Further, since your child is a U.S. citizen, and was in your wife's custody, you can still claim him/her as a dependent.

If you need professional help filing your return, double-click on my title and then scroll down to my profile, where you will find my email address and website links.