Assuming these are main crop potatoes, bit late for 2nd early potatoes, then you should be able to lift them now. We've lifted most of ours aside from a very late cropper.

i was always told that if the potatoes have flowered, then they are ready to pick, or you could scrape the dirt away from the side of aplant and see what they look like

How main crop flowered long before they were ready to lift. Rule of thumb is 17 weeks from planting.