Well not all schools use computers and they're all different, regardless. I'd say though that you will have some trouble getting in with a 2.8 science unless you have significant improvement toward the end and/or were taking some really difficult math or engineering courses.
Some schools can definitely throw you out right away. But, it really depends. Although your GPAs are not too high, if you have an exceptionally high MCAT score to make up for your GPA, you might be able to get past the number screening. But, each school has a different policy on this, so I cannot say this for sure though.
Search the boards to find which schools might not have auto cutoffs, then add some of those to your list. With a good mcat u have a chance. I too had an uphill battle w/ gpa, but came out on top.