Where are you coming from, ie. will you have had a long journey? Because if you want to hang out anywhere until the following morning, Playa is the place to do it.
If you don't stop over, then so long as formalities at CUN don't take too long you should manage to get to the last flight from Corozal-San Pedro. I don't think you'll have a lot of time to spare though. Best pre-arrange with Henry Menzies (www.belizetransfers.com
)) to meet you at Chetumal bus station - if it's possible to get you to your flight he'll do it.