Best place to vacation in Mexico?

[playin2gthr]

My wife and I are a late 30's early 40's couple. We'd appreciate any advice as to where to vacation in Mexico. Neither of us are in to the bar scene/nightlife type of thing that Cancun offers. We are not shoppers, so we have no interest in being somewhere where there's lots of shops to browse through. We are looking for a more relaxed atmosphere, at an all inclusive resort located along the beach (preferably adults only). We both scuba dive, so we'd like an area that has good waters for diving. If we can find something like that which also has nice scenic areas nearby with tour trips, that would be cool. We are a very relaxed couple, and not in to large crowds and lots of noise. We went to the El Dorado Royale 2 yrs ago, and it was nice, but we'd like somewhere where the water is a little clearer and nicer. We would appreciate some advice from experienced travelers. (WE have also been to Cozumel, and it was nice too, but we are looking for other options for our upcoming vacation).
Also, please let us know what time of the year you think is the best to travel to any destination you suggest. I know that going at the right time of year can make all the difference.

We have heard Puerto Vallarta is nice, any thoughts on that?

 

[mexicanchild]

I say at the beaches of Mexico