I have heard differing answers for this, so I wanted to see if there is a consensus.

Is there a general rule of thumb for draw weight?  For example if a bow is listed as 60# @ 30 inches, and I have a 28# draw, what is the conversion?  I have heard 5lbs per inch, all the way down to 2lbs.    Thanks.

the general rule of thumb is 3lb per extra inch of draw weight

Like Rob said 3 pounds per inch is kind of the standard but I think it depends on the bow and the way it was tillered.  I have some bows that stack 3 pounds per inch and a couple that feels like you hit a wall anything after 28 inches.  I would check with the bowyer if possible and see what he says about the way his bows are tillered.

This is the right place for a Dumb....?....        
   As mentioned above 3# is a good standard....
So your pulling around 54#....

60# 30" sounds like a custom bow as the standard is 28" # the bow may shoot okay but probably its best performance will be at the 30" it was designed for.