Mexico beaches/resorts? Which one??

[dealmaker]

So heading down to Mexico City next spring and after that want to do a week's R&R in one of the better resorts (i.e not Acapulco etc) with entire family.

So any recommendations for any nice resorts on a beach ?? Seems all the bright young things from the US head to Cabo San Lucas - what about that or Puerto Vallarta or even Cancun??

Not done any beaches there so need some suggestions - is East/Caribbean coast better - or West coast??

Thanks!