Spent time in Manzanillo 15 years ago. One of our very favorite areas. It doesn't resemble Tijuana in any way!
Manzanillo was a nice "non-touristy" city full of friendly people. We spent time at the resort areas at Club Santiago, a complete resort with people from all over the world. The setting on the water reminded us of the Spanish Riviera. Also there's Las Hadas, the spectacular resort that reminded us of Monaco with its sparkling marina and unusual architecture. We're not "beach" people, but do enjoy seeing how the jet set lives, as well as seeing how the real Mexican families live.