Wesin in Puerto Vallarta just became a Cat 2 -- probably the best deal out there. Bring some food (non-beef products) and can buy US prodcucts in the supermarket.
Otherwise, Cabo San Lucas hotels are Cat 4 -- and there is Chabad in Cabo that sells food (though very expensive), and Costco sells deli meat (when they have it in stock).
Cancun is cancun -- I wouldn't go back there if you paid me (well, maybe if you paid me in SPG points I'd consider
)