My wife and I have been on 11 cruises, 2 on Carnaval (constant party scene), 2 on Princess, 7 on Celebrity.
Would go on Carnaval again if you were paying for the trip. didn't care for the food or service on Princess, really liked Celebrity.
Only cruise on left coast was with Princess to the Mexican riviera. Puerto Vallarta is nice, Mazatlin is a dump, and were only in Cabo for half a day. Calling that trip the riviera is like calling Long Beach a garden spot.
See if you can work out a deal to the Caribbean.