Looking for cheapest vacation options in Playa Del Carmen Mexico?

We are travelling to the Cancun area in mid-March for one week, we have booked our flights and the first 2 days to Cancun. We are trying to find the best way top stay in Riviera Maya for the next five nights. We found that all good resorts charge at least around $400 per night all inclusive for a 4 star resort (2 adults + 2 kids) for an ocean view room.
Any suggestion on how to better alternatives (renting a condo and dinning out??).
Please help us with your suggestions.

Thanks
Ken