I'm always surprised that the west coast of Mexico is usally overlooked by Brits and Europeans. I suppose it has a lot to do with the airfares and connections. However, the Pacific Ocean beaches are far superior to those found on the east coast, in my opinion. For one, many of the smaller cities on the west coast are still fairly uncluttered. Manzanillo, for one has beautiful beaches that are bound on the coastal side by spectacular cliffs and coves. The Manzanillo area is on the same latitude as Hawaii and the ocean is a brillant blue. The "destinations" such as Vallarta and Acapulco are often crowded just as is Cancun. However, even those beach cities don't suffer the influx of college students on spring break around the end of March and into April.
One of the most active volcanos in Mexico is near Manzanillo in the colonial State of Colima. There are numerous ancient Missions nearby from the earliest days of the Spanish conquest. Take a look here:
http://www.gomanzanillo.com/beaches/index.htm ...
At any rate, we've enjoyed it numerous times. (The seafood is unmatched, by the way).