Shall we file the Tax jointly?

My wife used to have H-1,but she got laid off last Feb from and got a job in China .She was in the US for less than 4 months last year and just had very little income (2000.00).I was in the US for the entire 2003.I am in H-1.
Should we file Tax return jointly or seperately? Do I have to count how many days she was here in 2003 or just assume she was here for the whole year? Please give me some help.Thanks.