I will admit that BJJ does give some great ideas on the ground, as well as methods to get back up properly and safely. However, the goal, in the situation you just presented, should be to get back to your feet ASAP. From that point, I like the idea of trying to a) position yourself so you try to use one person as a shield against the others, and b) doing your best to cause as much damage to the person closest to you.
To clarify my above. Trying to use 1 opponent to block the others. Will it always work? Nothing is a sure shot, but its a good tool to use and will hopefully frustrate the others. If you can overwhelm the person closest to you, grabbing them if necessary, that may be enough to make the others think twice, if they see their friend in pain.
