We love Cozumel, and have visited it twice so far. The beach we went to was amazing and the colour of the water was beyond beautiful!
On the west coast we prefer Puerto Vallarta over Cabo or Mazatlan. As soon as we stepped off the ship in PV we really liked it. The waves crashing along the Malecon were great. We loved all the statues, local artists, and the vendors selling the touristy carvings and painted bowls.
PV was great, but Cozumel is the winner for me.
So, do you have a favourite Mexican port?