NO this is not a mandatory all-inclusive, unless you booked the resort that way from a travel site.
No walking to Puerto Morales. The resort is very remote, cab fare will be 4.00US. I think possibly by now a bus might be running by the resort.
You will be right in between Cancun and Playa Del Carmen.
I do not believe there is a grocery store in Puerto Morales. I do believe food will be very expensive at the resort.
You can take a cab to highway and then a bus to Playa to Walmart for supplies. I am sure a cab to Playa will be 30.00 US.
try to line up your airport transportation to the resort before you arrive.
I would think 16.00 per person each way.
Good News is the resort is very very rich and famous.