1) Dig your way out.
Considering, from what we saw, the group isn’t in any immediate danger from the horde, if I don’t see Daryl, or Carol, or somebody at least try to start moving all the rubble out of the way and try to go back out the way they came in…I’m gonna be irritated.
When you look at the options we saw Daryl and company were left with, it looks like they can either try to dig their way out, or…try to make a go against the horde (Don’t worry, I’ll get to that). Given those options, digging their way seems like the better one, wouldn’t you say?
Now, I know that there’s a good chance that some of the rubble at the cave entrance may be just too damn big for the group to move without a lever of some kind, but, definitely not all of it. Wherever there’s rocks small enough that the group can move (So long as it won’t obviously cause a further cave-in), they should try to pry out of the rubble and make a hole for themselves…and probably have to fight their way through the Whisperers, who, I’d imagine, are waiting for them.
There’s no elaborate explanations here. The way out of bad situations may not be easy, but sometimes, it is simple.