Do the drivers have to stop for you as long as ur in the pick up areas or is it only at the signs along the route

They may stop anywhere along the route if you hail them, but they will not stop if they are in an unsafe position (cross traffic, traffic behind, etc) They are only required to stop at designated sign locations if someone is standing there.

Some places don't have the signs

They will stop when you hail them when it is safe to stop. Safe places to stop often don't have designated stop signs along the route.

Only at the signs