I think it depends on the size light fixture you are planning on having. For example, our island is going to be 75"x28" approximately and we are using 3 lights. But our lights are very narrow (I think about 3") and the light is more focused rather than wide.

Not knowing what you are planning on using, I would probably try to have a pendant over the shorter side of the L and probably 3 lights over the long side. But again, it depends on the pendant size and light spread.