Can I safely clean/eat harvested foods that have aphids on them?
The best way to remove the aphids is to submerge the vegetables in cold water for at least 10 minutes.  Then drain, rinse them off, and dry them.  Salad spinners are perfect for this.

Once the aphids have been drowned and rinsed off, the greens are perfectly safe to eat.  Actually, it should be safe to eat the aphids as well, it's just unappetizing.