Let me see if I understand what is going on. Negan and his followers left Rick and his remaining group, less Darryl, where they were with the camper and told them he would return in a week for his tribute from them.
The obvious question is why in the hell wouldn't the group load up and put a week's distance between themselves and Negan? Am I missing something here? Darryl is being held captive, Glenn and Abraham are dead; he has Rosita, Maggie, Sasha, Eugene and Coral to resist Negan and his thugs. Are they all stupid? Why not leave and hide out until they can find another group and then return in force? It may be the apocalypse, but it ain't rocket surgery.
Here's my logic against that course.
1) With Maggie's illness/complications, she is a liability on a road trip. And, who knows when they might run into a doctor? As it is, she's headed to the hill top, where there is known medical help. This means the group is down at least one more member as someone needs to assist her. So do you take Maggie with or not?
2) What route to take? Whatever route they originally took to get to Alexandria is out; no friendlies that way. Who knows the extent of Negan's reach in whatever other direction they take? Who knows that he doesn't have some lookouts with radios keeping tabs on the group as they leave?
3) How far do they have to go to find enough people to fight Negan? What's their recruiting pitch to said people?
4) Say they do build a bigger group and come back. How many people does Negan have? What's his location? Rick sure doesn't know.
5) Unless I've missed something, Negan isn't coming back to that clearing in a week, he's coming to Alexandria. If Rick's group high-tails it, they're writing off the inhabitants of Alexandria. They are also possibly writing off Daryl. And, if they decided not to take Maggie with them, then they're written her off because Negan knows about the hill top too.
6) If they're leaving immediately, I don't think they have a lot of supplies on hand.
To me, if they're going to bug out of that area it should be with no expectations of returning anytime soon and with the knowledge that people they know and/or care about will die, or at least be severely handled because of their decision of leaving.